From d3ddb0822bd516e2e2c38eb26f17cad815109df4 Mon Sep 17 00:00:00 2001
From: Dennis Korpel <dkorpel@gmail.com>
Date: Wed, 3 Jun 2026 11:01:06 +0200
Subject: [PATCH 1/7] Run test suite with druntime, not Phobos

The dmd test suite is supposed to be independent of Phobos.
Consolidate ^^ related tests, and only link Phobos if a test has
RUNNABLE_PHOBOS_TEST or COMPILABLE_MATH_TEST set.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 compiler/test/compilable/b19294.d             |   1 +
 compiler/test/compilable/compile1.d           |   5 +-
 compiler/test/compilable/ddoc24871.d          |   4 +-
 .../test/compilable/extra-files/json2.json    |   5 +-
 compiler/test/compilable/paranoia_ctfe.d      |   1 +
 compiler/test/fail_compilation/b3841.d        |   9 -
 compiler/test/fail_compilation/diag10327.d    |   5 +-
 compiler/test/fail_compilation/fail18938.d    |   1 +
 compiler/test/fail_compilation/fail21045.d    |   5 +-
 compiler/test/fail_compilation/fail21091a.d   |   5 +-
 compiler/test/fail_compilation/fail21091b.d   |   5 +-
 compiler/test/fail_compilation/ice7782.d      |   5 +-
 compiler/test/fail_compilation/issue11070.d   |   3 +-
 compiler/test/fail_compilation/test22361.d    |   5 +-
 compiler/test/run.d                           |  65 +++--
 compiler/test/runnable/argufilem.d            |   3 +-
 compiler/test/runnable/arrayop.d              |   1 -
 compiler/test/runnable/ctortests.d            | 119 +++++++++
 compiler/test/runnable/dhry.d                 |   1 -
 .../test/runnable/extra-files/importc_main.d  |   4 +-
 .../test/runnable/extra-files/importc_main2.d |   1 -
 compiler/test/runnable/imports/argufile.d     |  14 +-
 compiler/test/runnable/link11069b.d           |   1 +
 compiler/test/runnable/paranoia.d             |   1 +
 .../test/runnable/{ctorpowtests.d => pow.d}   | 247 ++++++++++--------
 compiler/test/runnable/test13117.d            |   1 +
 compiler/test/runnable/test13117b.d           |   1 +
 compiler/test/runnable/test18076.sh           |   2 +-
 compiler/test/runnable/test19.d               |   4 +-
 compiler/test/runnable/test5943.d             |  77 ------
 compiler/test/runnable/test8544.d             |   8 +-
 compiler/test/runnable/test9287.sh            |   2 +-
 compiler/test/runnable/testabi.d              |   2 +-
 compiler/test/runnable/xtest46.d              |  28 --
 compiler/test/tools/d_do_test.d               |  23 +-
 35 files changed, 368 insertions(+), 296 deletions(-)
 create mode 100644 compiler/test/runnable/ctortests.d
 rename compiler/test/runnable/{ctorpowtests.d => pow.d} (58%)
 delete mode 100644 compiler/test/runnable/test5943.d

diff --git a/compiler/test/compilable/b19294.d b/compiler/test/compilable/b19294.d
index ed1a71747e40..69a425a13d3c 100644
--- a/compiler/test/compilable/b19294.d
+++ b/compiler/test/compilable/b19294.d
@@ -1,3 +1,4 @@
+// COMPILABLE_MATH_TEST
 alias MT = MyStruct!int;
 
 struct MyStruct(T)
diff --git a/compiler/test/compilable/compile1.d b/compiler/test/compilable/compile1.d
index f0b6dffe3622..85caa8088582 100644
--- a/compiler/test/compilable/compile1.d
+++ b/compiler/test/compilable/compile1.d
@@ -1,10 +1,9 @@
-// COMPILABLE_MATH_TEST
 // PERMUTE_ARGS:
 // REQUIRED_ARGS: -verrors=simple
 // EXTRA_FILES: imports/a12506.d
 /* TEST_OUTPUT:
 ---
-compilable/compile1.d(231): Deprecation: use of complex type `cdouble` is deprecated, use `std.complex.Complex!(double)` instead
+compilable/compile1.d(230): Deprecation: use of complex type `cdouble` is deprecated, use `std.complex.Complex!(double)` instead
 ---
 */
 
@@ -872,8 +871,6 @@ alias TT14166(T...) = T;
 static assert(is(typeof((s14166.x += 1) = 2) == int));     // ok <- error
 static assert(is(typeof(s14166.a.length += 2) == size_t)); // ok <- error
 static assert(is(typeof(s14166++) == S14166));             // ok <- error
-static assert(is(typeof(s14166.x ^^ 2) == int));           // ok <- error
-static assert(is(typeof(s14166.y ^^= 2.5) == double));     // ok <- error
 static assert(is(typeof(makeAA14166()[0] = 1) == X14166)); // ok <- error
 static assert(is(typeof(tup14166.field = makeTup14166()) == TT14166!(int, int))); // ok <- error
 
diff --git a/compiler/test/compilable/ddoc24871.d b/compiler/test/compilable/ddoc24871.d
index 98bd36dce6eb..97591346e945 100644
--- a/compiler/test/compilable/ddoc24871.d
+++ b/compiler/test/compilable/ddoc24871.d
@@ -2,7 +2,7 @@
 // REQUIRED_ARGS: -D -Dd${RESULTS_DIR}/compilable -o-
 // POST_SCRIPT: compilable/extra-files/ddocAny-postscript.sh
 // EXTRA_SOURCES: extra-files/ddoc_minimal.ddoc
-import std.stdio;
+import core.stdc.stdio;
 
 /// Example
 /// ---
@@ -14,6 +14,6 @@ import std.stdio;
 /// ---
 void main() {
 
-    writeln("Hello, World!");
+    printf("Hello, World!\n");
 
 }
diff --git a/compiler/test/compilable/extra-files/json2.json b/compiler/test/compilable/extra-files/json2.json
index e4ee50e71427..53fd87bf7ae9 100644
--- a/compiler/test/compilable/extra-files/json2.json
+++ b/compiler/test/compilable/extra-files/json2.json
@@ -8,8 +8,7 @@
         "defFile": null,
         "importPaths": [
             "compilable",
-            "../../druntime/import",
-            "../../../phobos"
+            "../../druntime/import"
         ],
         "libName": "VALUE_REMOVED_FOR_TEST",
         "libraryFiles": [
@@ -89,4 +88,4 @@
             }
         ]
     }
-}
+}
\ No newline at end of file
diff --git a/compiler/test/compilable/paranoia_ctfe.d b/compiler/test/compilable/paranoia_ctfe.d
index e48a6d1f4fd6..ed72263ec7de 100644
--- a/compiler/test/compilable/paranoia_ctfe.d
+++ b/compiler/test/compilable/paranoia_ctfe.d
@@ -1,3 +1,4 @@
+// COMPILABLE_MATH_TEST
 /*
 EXTRA_SOURCES: ../runnable/extra-files/paranoia.d
 REQUIRED_ARGS: -o- -version=CTFE
diff --git a/compiler/test/fail_compilation/b3841.d b/compiler/test/fail_compilation/b3841.d
index bbbb6c96d3c9..f3939d8cab0f 100644
--- a/compiler/test/fail_compilation/b3841.d
+++ b/compiler/test/fail_compilation/b3841.d
@@ -70,13 +70,4 @@ void main()
         f!(op, int, float)();
         f!(op, long, double)();
     }
-
-    // OK
-    f!("^^=", int, int)();
-    f!("^^=", long, int)();
-    f!("^^=", long, short)();
-    f!("^^=", float, long)();
-    f!("^^=", double, float)();
-    // Should that really be OK ?
-    f!("^^=", float, double)();
 }
diff --git a/compiler/test/fail_compilation/diag10327.d b/compiler/test/fail_compilation/diag10327.d
index 1366882edeb8..18de6dbb1fde 100644
--- a/compiler/test/fail_compilation/diag10327.d
+++ b/compiler/test/fail_compilation/diag10327.d
@@ -1,11 +1,10 @@
 /*
 TEST_OUTPUT:
 ---
-fail_compilation/diag10327.d(12): Error: unable to read module `test10327`
-fail_compilation/diag10327.d(12):        Expected 'imports/test10327.d' or 'imports/test10327/package.d' in one of the following import paths:
+fail_compilation/diag10327.d(11): Error: unable to read module `test10327`
+fail_compilation/diag10327.d(11):        Expected 'imports/test10327.d' or 'imports/test10327/package.d' in one of the following import paths:
 import path[0] = fail_compilation
 import path[1] = $p:druntime/import$
-import path[2] = $p:phobos$
 ---
 */
 
diff --git a/compiler/test/fail_compilation/fail18938.d b/compiler/test/fail_compilation/fail18938.d
index f7ece6daf809..59dd2b514305 100644
--- a/compiler/test/fail_compilation/fail18938.d
+++ b/compiler/test/fail_compilation/fail18938.d
@@ -1,3 +1,4 @@
+// RUNNABLE_PHOBOS_TEST
 // REQUIRED_ARGS: -c -Ifail_compilation/imports/
 // EXTRA_SOURCES: imports/test18938a/cache.d imports/test18938a/file.d
 // EXTRA_FILES: imports/test18938b/file.d
diff --git a/compiler/test/fail_compilation/fail21045.d b/compiler/test/fail_compilation/fail21045.d
index c43eda3f9729..0625780e3cba 100644
--- a/compiler/test/fail_compilation/fail21045.d
+++ b/compiler/test/fail_compilation/fail21045.d
@@ -1,11 +1,10 @@
 /*
 TEST_OUTPUT:
 ---
-fail_compilation/fail21045.d(12): Error: unable to read module `__stdin`
-fail_compilation/fail21045.d(12):        Expected '__stdin.d' or '__stdin/package.d' in one of the following import paths:
+fail_compilation/fail21045.d(11): Error: unable to read module `__stdin`
+fail_compilation/fail21045.d(11):        Expected '__stdin.d' or '__stdin/package.d' in one of the following import paths:
 import path[0] = fail_compilation
 import path[1] = $p:druntime/import$
-import path[2] = $p:phobos$
 ---
 */
 
diff --git a/compiler/test/fail_compilation/fail21091a.d b/compiler/test/fail_compilation/fail21091a.d
index c2bbe4d59e4d..5eebf872a3bc 100644
--- a/compiler/test/fail_compilation/fail21091a.d
+++ b/compiler/test/fail_compilation/fail21091a.d
@@ -3,11 +3,10 @@
 /*
 TEST_OUTPUT:
 ----
-fail_compilation/fail21091a.d(16): Error: unable to read module `Ternary`
-fail_compilation/fail21091a.d(16):        Expected 'Ternary.d' or 'Ternary/package.d' in one of the following import paths:
+fail_compilation/fail21091a.d(15): Error: unable to read module `Ternary`
+fail_compilation/fail21091a.d(15):        Expected 'Ternary.d' or 'Ternary/package.d' in one of the following import paths:
 import path[0] = fail_compilation
 import path[1] = $p:druntime/import$
-import path[2] = $p:phobos$
 ----
 */
 
diff --git a/compiler/test/fail_compilation/fail21091b.d b/compiler/test/fail_compilation/fail21091b.d
index 3d7d6001bd2a..1bef94359894 100644
--- a/compiler/test/fail_compilation/fail21091b.d
+++ b/compiler/test/fail_compilation/fail21091b.d
@@ -3,11 +3,10 @@
 /*
 TEST_OUTPUT:
 ----
-fail_compilation/fail21091b.d(16): Error: unable to read module `Tid`
-fail_compilation/fail21091b.d(16):        Expected 'Tid.d' or 'Tid/package.d' in one of the following import paths:
+fail_compilation/fail21091b.d(15): Error: unable to read module `Tid`
+fail_compilation/fail21091b.d(15):        Expected 'Tid.d' or 'Tid/package.d' in one of the following import paths:
 import path[0] = fail_compilation
 import path[1] = $p:druntime/import$
-import path[2] = $p:phobos$
 ----
 */
 
diff --git a/compiler/test/fail_compilation/ice7782.d b/compiler/test/fail_compilation/ice7782.d
index 551933b382d2..9fccbf821867 100644
--- a/compiler/test/fail_compilation/ice7782.d
+++ b/compiler/test/fail_compilation/ice7782.d
@@ -2,11 +2,10 @@
 EXTRA_FILES: imports/ice7782algorithm.d imports/ice7782range.d
 TEST_OUTPUT:
 ----
-fail_compilation/ice7782.d(14): Error: unable to read module `ice7782math`
-fail_compilation/ice7782.d(14):        Expected 'imports/ice7782range/imports/ice7782math.d' or 'imports/ice7782range/imports/ice7782math/package.d' in one of the following import paths:
+fail_compilation/ice7782.d(13): Error: unable to read module `ice7782math`
+fail_compilation/ice7782.d(13):        Expected 'imports/ice7782range/imports/ice7782math.d' or 'imports/ice7782range/imports/ice7782math/package.d' in one of the following import paths:
 import path[0] = fail_compilation
 import path[1] = $p:druntime/import$
-import path[2] = $p:phobos$
 ----
 */
 
diff --git a/compiler/test/fail_compilation/issue11070.d b/compiler/test/fail_compilation/issue11070.d
index 07d69ee87ab5..fbba387d686c 100644
--- a/compiler/test/fail_compilation/issue11070.d
+++ b/compiler/test/fail_compilation/issue11070.d
@@ -1,14 +1,13 @@
 /*
 TEST_OUTPUT:
 ---
-fail_compilation/issue11070.d(16): Error: undefined identifier `x`
+fail_compilation/issue11070.d(15): Error: undefined identifier `x`
 ---
 */
 
 int get() { return 1; }
 
 void test() {
-    import std.stdio : writeln;
     switch (auto x = get()) {
         default:
             auto z = x;
diff --git a/compiler/test/fail_compilation/test22361.d b/compiler/test/fail_compilation/test22361.d
index 11255ff1f1b0..e375a29e648c 100644
--- a/compiler/test/fail_compilation/test22361.d
+++ b/compiler/test/fail_compilation/test22361.d
@@ -1,11 +1,10 @@
 /*
 TEST_OUTPUT:
 ---
-fail_compilation/test22361.d(11): Error: unable to read module `this_module_does_not_exist`
-fail_compilation/test22361.d(11):        Expected 'this_module_does_not_exist.d' or 'this_module_does_not_exist/package.d' in one of the following import paths:
+fail_compilation/test22361.d(10): Error: unable to read module `this_module_does_not_exist`
+fail_compilation/test22361.d(10):        Expected 'this_module_does_not_exist.d' or 'this_module_does_not_exist/package.d' in one of the following import paths:
 import path[0] = fail_compilation
 import path[1] = $p:druntime/import$
-import path[2] = $p:phobos$
 ---
 */
 import this_module_does_not_exist;
diff --git a/compiler/test/run.d b/compiler/test/run.d
index 9ac44ffec768..f59fa7b3b3f8 100755
--- a/compiler/test/run.d
+++ b/compiler/test/run.d
@@ -145,6 +145,7 @@ Options:
     }
 
     verifyCompilerExists(env);
+    ensureDruntime(env);
     prepareOutputDirectory(env);
 
     if (runUnitTests)
@@ -227,6 +228,30 @@ void verifyCompilerExists(const string[string] env)
     }
 }
 
+/**
+Builds (or rebuilds) the druntime library that the tests link against.
+
+Prevent test failures due to forgetting to make druntime manually.
+*/
+void ensureDruntime(const string[string] env)
+{
+    const make = environment.get("MAKE", "make");
+    const druntimeDir = environment.get("DRUNTIME_PATH", testPath(buildPath("..", "..", "druntime")));
+    const buildCommand = [
+        make, "-C", druntimeDir,
+        "MODEL=" ~ env["MODEL"],
+        "BUILD=" ~ env["BUILD"],
+    ];
+
+    writefln("Building druntime: %-(%s %)", buildCommand);
+    stdout.flush();
+    if (spawnProcess(buildCommand, env, Config.none, scriptDir).wait)
+    {
+        stderr.writeln("failed to build druntime");
+        quitSilently(1);
+    }
+}
+
 /// Creates the necessary directories and files for the test runner(s)
 void prepareOutputDirectory(const string[string] env)
 {
@@ -286,29 +311,20 @@ void ensureToolsExists(const string[string] env, const TestTool[] tools ...)
         auto lastModifiedBin = targetBin.timeLastModified.ifThrown(SysTime.init);
         if (lastModifiedBin >= sourceFile.timeLastModified)
         {
-            auto lastModifiedDmd = env["DMD"].timeLastModified.ifThrown(SysTime.init);
-            if (!tool.linksWithTests || lastModifiedBin >= lastModifiedDmd)
-            {
-                log("%s is already up-to-date", tool);
-                continue;
-            }
+            log("%s is already up-to-date", tool);
+            continue;
         }
 
         string[] buildCommand;
-        bool overrideEnv;
         if (tool.linksWithTests)
         {
-            // This will compile the dshell library thus needs the actual
-            // DMD compiler under test
             buildCommand = [
-                env["DMD"],
-                "-conf=",
+                hostDMD,
                 "-m"~env["MODEL"],
                 "-of" ~ targetBin,
                 "-c",
                 sourceFile
             ] ~ getPicFlags(env);
-            overrideEnv = true;
         }
         else
         {
@@ -322,7 +338,7 @@ void ensureToolsExists(const string[string] env, const TestTool[] tools ...)
 
         writefln("Executing: %-(%s %)", buildCommand);
         stdout.flush();
-        if (spawnProcess(buildCommand, overrideEnv ? env : null).wait)
+        if (spawnProcess(buildCommand, null).wait)
         {
             stderr.writefln("failed to build '%s'", targetBin);
             atomicOp!"+="(failCount, 1);
@@ -551,20 +567,25 @@ string[string] getEnvironment()
     env["BUILD"] = build;
     env["EXE"] = exeExtension;
     env["DMD"] = dmdPath;
+    env["HOST_DMD"] = hostDMD;
     env.setDefault("DMD_TEST_COVERAGE", "0");
 
     const generatedSuffix = "generated/%s/%s/%s".format(os, build, model);
 
+    const druntimePath = environment.get("DRUNTIME_PATH", projectRootDir.buildPath("druntime"));
+    const druntimeLibDir = generatedDir.buildPath(os, build, model);
+
+    const phobosPath = environment.get("PHOBOS_PATH", projectRootDir.dirName.buildPath("phobos"));
+
     version(Windows)
     {
         env.setDefault("ARGS", "-inline -release -g -O");
         env["OBJ"] = ".obj";
         env["DSEP"] = `\\`;
         env["SEP"] = `\`;
-        auto druntimePath = environment.get("DRUNTIME_PATH", testPath(`..\..\druntime`));
-        auto phobosPath = environment.get("PHOBOS_PATH", testPath(`..\..\..\phobos`));
-        env["DFLAGS"] = `-I"%s\import" -I"%s"`.format(druntimePath, phobosPath);
-        env["LIB"] = phobosPath ~ ";" ~ environment.get("LIB");
+        env["DFLAGS"] = `-I"%s\import" -defaultlib=druntime -debuglib=druntime`.format(druntimePath);
+        env["LIB"] = druntimeLibDir ~ ";" ~ environment.get("LIB");
+        env["PHOBOS_DFLAGS"] = `-I"%s\import" -I"%s"`.format(druntimePath, phobosPath);
     }
     else
     {
@@ -572,8 +593,6 @@ string[string] getEnvironment()
         env["OBJ"] = ".o";
         env["DSEP"] = "/";
         env["SEP"] = "/";
-        auto druntimePath = environment.get("DRUNTIME_PATH", testPath(`../../druntime`));
-        auto phobosPath = environment.get("PHOBOS_PATH", testPath(`../../../phobos`));
 
         // default to PIC, use PIC=1/0 to en-/disable PIC.
         // Note that shared libraries and C files are always compiled with PIC.
@@ -582,11 +601,13 @@ string[string] getEnvironment()
             pic = false;
 
         env["PIC_FLAG"]  = pic ? "-fPIC" : "";
-        env["DFLAGS"] = "-I%s/import -I%s".format(druntimePath, phobosPath)
-            ~ " -L-L%s/%s".format(phobosPath, generatedSuffix);
+        env["DFLAGS"] = "-I%s/import -defaultlib=druntime -debuglib=druntime".format(druntimePath)
+            ~ " -L-L%s".format(druntimeLibDir);
+
+        env["PHOBOS_DFLAGS"] = "-I%s/import -I%s -L-L%s/%s".format(druntimePath, phobosPath, phobosPath, generatedSuffix);
         bool isShared = environment.get("SHARED") != "0" && os.among("linux", "freebsd", "hurd") > 0;
         if (isShared)
-            env["DFLAGS"] = env["DFLAGS"] ~ " -defaultlib=libphobos2.so -L-rpath=%s/%s".format(phobosPath, generatedSuffix);
+            env["PHOBOS_DFLAGS"] = env["PHOBOS_DFLAGS"] ~ " -defaultlib=libphobos2.so -L-rpath=%s/%s".format(phobosPath, generatedSuffix);
 
         if (pic)
             env["REQUIRED_ARGS"] = environment.get("REQUIRED_ARGS") ~ " " ~ env["PIC_FLAG"];
diff --git a/compiler/test/runnable/argufilem.d b/compiler/test/runnable/argufilem.d
index f4636365c6ca..a2c015ec3162 100644
--- a/compiler/test/runnable/argufilem.d
+++ b/compiler/test/runnable/argufilem.d
@@ -15,12 +15,13 @@ why is 8 scared of 7? because789
 // main.d -------------------------------------------------------
 
 import argufile;
+import core.stdc.stdio : printf;
 
 int main(string[] args)
 {
         string message = arguments("bob is ", 7, " years old");
 
-        writefln(message);
+        printf("%.*s\n", cast(int) message.length, message.ptr);
 
         argufile.useargs(); // will crash here
 
diff --git a/compiler/test/runnable/arrayop.d b/compiler/test/runnable/arrayop.d
index 4c0836a96dc8..11bf910846a5 100644
--- a/compiler/test/runnable/arrayop.d
+++ b/compiler/test/runnable/arrayop.d
@@ -1,5 +1,4 @@
 // RUNNABLE_PHOBOS_TEST
-import std.math;
 
 extern(C) int printf(const char*, ...);
 
diff --git a/compiler/test/runnable/ctortests.d b/compiler/test/runnable/ctortests.d
new file mode 100644
index 000000000000..74f0608dec5f
--- /dev/null
+++ b/compiler/test/runnable/ctortests.d
@@ -0,0 +1,119 @@
+// PERMUTE_ARGS:
+//
+// CTFE constructor / copy-constructor tests.
+// The `^^` (pow) parts that used to live here are in runnable/pow.d.
+
+int magicVariable()
+{
+    if (__ctfe)
+        return 3;
+
+    shared int var = 2;
+    return var;
+}
+
+static assert(magicVariable()==3);
+
+// https://issues.dlang.org/show_bug.cgi?id=3535
+struct StructWithCtor
+{
+    this(int _n) {
+        n = _n; x = 5;
+    }
+    this(int _n, float _x) {
+        n = _n; x = _x;
+    }
+    int n;
+    float x;
+}
+
+enum A = StructWithCtor(1);
+enum B = StructWithCtor(7, 2.3);
+
+static assert(A.n == 1);
+static assert(A.x == 5.0);
+static assert(B.n == 7);
+static assert(B.x == 2.3);
+
+// Test copy constructors
+struct CopyTest {
+   double x;
+   this(double a) { x = a * 10.0;}
+   this(this) {  x+=2.0;}
+}
+
+struct CopyTest2
+{
+   int x; int x1; int x2; int x3;
+   this(int a) { x = a * 2; x1 = 3;}
+   this(this) {  x1+=17;}
+}
+
+
+const CopyTest z = CopyTest(5.3);
+/+
+// TODO: This is not yet supported. But it
+// generates an error message instead of wrong-code.
+const CopyTest w = z;
+static assert(z.x==55.0);
++/
+
+int copytest1()
+{
+   CopyTest z = CopyTest(3.4);
+   CopyTest w = z;
+   assert(w.x == 36.0);
+   CopyTest2 q = CopyTest2(7);
+   CopyTest2 q2 = q;
+   CopyTest2 q3 = q2;
+   assert(q3.x1 == 37);
+
+  return 123;
+}
+static assert(copytest1()==123);
+
+// This must not cause a segfault
+alias int FILTH;
+struct Filth
+{
+     struct Impl
+    {
+        FILTH * handle = null;
+        this(FILTH* h, uint r, string n)
+        {
+            handle = h;
+        }
+    }
+    Impl * p;
+
+    this(string name, in char[] stdioOpenmode = "rb")
+    {
+    }
+
+    ~this()
+    {
+        if (!p) return;
+    }
+
+    this(this)
+    {
+        if (!p) return;
+    }
+    }
+    struct InputByChar
+    {
+        private Filth _f;
+
+        this(Filth f)
+        {
+            _f = f;
+        }
+}
+
+/************************************/
+
+void main()
+{
+    assert(!__ctfe);
+    assert(magicVariable()==2);
+}
diff --git a/compiler/test/runnable/dhry.d b/compiler/test/runnable/dhry.d
index 598feda290d6..3c5a8cb3fad4 100644
--- a/compiler/test/runnable/dhry.d
+++ b/compiler/test/runnable/dhry.d
@@ -343,7 +343,6 @@ Deprecation caused by https://issues.dlang.org/show_bug.cgi?id=20645
 import core.stdc.stdio;
 import core.stdc.string;
 import core.stdc.stdlib;
-import std.string;
 
 
 /* Compiler and system dependent definitions: */
diff --git a/compiler/test/runnable/extra-files/importc_main.d b/compiler/test/runnable/extra-files/importc_main.d
index 2b36d3b09aba..ef1d18cad4c1 100644
--- a/compiler/test/runnable/extra-files/importc_main.d
+++ b/compiler/test/runnable/extra-files/importc_main.d
@@ -1,11 +1,11 @@
 
-import std.stdio;
+import core.stdc.stdio;
 import importc_test;
 
 int main()
 {
     auto rc = someCodeInC(3, 4);
-    writeln("Result of someCodeInC(3,4) = ", rc );
+    printf("Result of someCodeInC(3,4) = %d\n", rc);
     assert( rc == 7, "Wrong result");
     return 0;
 }
diff --git a/compiler/test/runnable/extra-files/importc_main2.d b/compiler/test/runnable/extra-files/importc_main2.d
index 598d0f936d8b..f534840d7e3c 100644
--- a/compiler/test/runnable/extra-files/importc_main2.d
+++ b/compiler/test/runnable/extra-files/importc_main2.d
@@ -1,5 +1,4 @@
 
-import std.stdio;
 import importc_test;
 
 int main()
diff --git a/compiler/test/runnable/imports/argufile.d b/compiler/test/runnable/imports/argufile.d
index 47a047494b47..fa397e8b5c32 100644
--- a/compiler/test/runnable/imports/argufile.d
+++ b/compiler/test/runnable/imports/argufile.d
@@ -3,17 +3,16 @@
 public:
 
 import core.vararg;
-import std.stdio;
-import std.utf;
+import core.stdc.stdio : printf;
 
-dstring formatstring(TypeInfo[] arguments, va_list argptr)
+string formatstring(TypeInfo[] arguments, va_list argptr)
 {
 
-	dstring message = null;
+	string message = null;
 
 	void putc(dchar c)
 	{
-		message ~= c;
+		message ~= cast(char) c;
 	}
 
 
@@ -25,15 +24,14 @@ dstring formatstring(TypeInfo[] arguments, va_list argptr)
 
 string arguments(...) // turns a bunch of arguments into a formatted char[] string
 {
-	return std.utf.toUTF8(formatstring(_arguments, _argptr));
+	return formatstring(_arguments, _argptr);
 }
 
 void useargs(...)
 {
 	string crashage = arguments("why is 8 scared of 7? because", 7,8,9);
 
-	//printf("%.*s\n", crashage);
-	writefln(crashage);
+	printf("%.*s\n", cast(int) crashage.length, crashage.ptr);
 }
 
 enum Mangle : char
diff --git a/compiler/test/runnable/link11069b.d b/compiler/test/runnable/link11069b.d
index 33992d177b37..b734d93439b0 100644
--- a/compiler/test/runnable/link11069b.d
+++ b/compiler/test/runnable/link11069b.d
@@ -1,3 +1,4 @@
+// RUNNABLE_PHOBOS_TEST
 // COMPILE_SEPARATELY:
 // EXTRA_SOURCES: imports/link11069x.d
 // EXTRA_SOURCES: imports/link11069y.d
diff --git a/compiler/test/runnable/paranoia.d b/compiler/test/runnable/paranoia.d
index 24d26546ba0a..7466616eabeb 100644
--- a/compiler/test/runnable/paranoia.d
+++ b/compiler/test/runnable/paranoia.d
@@ -1,3 +1,4 @@
+// RUNNABLE_PHOBOS_TEST
 /*
 EXTRA_SOURCES: extra-files/paranoia.d
 PERMUTE_ARGS:
diff --git a/compiler/test/runnable/ctorpowtests.d b/compiler/test/runnable/pow.d
similarity index 58%
rename from compiler/test/runnable/ctorpowtests.d
rename to compiler/test/runnable/pow.d
index 1df39babc812..f002e3e0a457 100644
--- a/compiler/test/runnable/ctorpowtests.d
+++ b/compiler/test/runnable/pow.d
@@ -1,18 +1,89 @@
+// Consolidated tests for the `^^` (pow) operator.
+//
+// `^^` lowers to `object._d_pow`, which still imports `std.math` internally
+// (see the TODO in druntime's object.d), so Phobos is needed on the link line
+// until that hook is moved into druntime.
 // RUNNABLE_PHOBOS_TEST
 // PERMUTE_ARGS:
 
-int magicVariable()
+// runtime `^^` with a runtime exponent
+
+__gshared uint x0 = 0;
+__gshared uint x1 = 1;
+__gshared uint x2 = 2;
+__gshared uint x3 = 3;
+__gshared uint x4 = 4;
+__gshared uint x5 = 5;
+__gshared uint x6 = 6;
+__gshared uint x7 = 7;
+__gshared uint x10 = 10;
+__gshared uint x15 = 15;
+__gshared uint x31 = 31;
+__gshared uint x32 = 32;
+
+void test5943()
 {
-    if (__ctfe)
-        return 3;
-
-    shared int var = 2;
-    return var;
+    assert(2 ^^ x0 == 1);
+    assert(2 ^^ x1 == 2);
+    assert(2 ^^ x31 == 0x80000000);
+    assert(4 ^^ x0 == 1);
+    assert(4 ^^ x1 == 4);
+    assert(4 ^^ x15 == 0x40000000);
+    assert(8 ^^ x0 == 1);
+    assert(8 ^^ x1 == 8);
+    assert(8 ^^ x10 == 0x40000000);
+    assert(16 ^^ x0 == 1);
+    assert(16 ^^ x1 == 16);
+    assert(16 ^^ x7 == 0x10000000);
+    assert(32 ^^ x0 == 1);
+    assert(32 ^^ x1 == 32);
+    assert(32 ^^ x6 == 0x40000000);
+    assert(64 ^^ x0 == 1);
+    assert(64 ^^ x1 == 64);
+    assert(64 ^^ x5 == 0x40000000);
+    assert(128 ^^ x0 == 1);
+    assert(128 ^^ x1 == 128);
+    assert(128 ^^ x4 == 0x10000000);
+    assert(256 ^^ x0 == 1);
+    assert(256 ^^ x1 == 256);
+    assert(256 ^^ x3 == 0x1000000);
+    assert(512 ^^ x0 == 1);
+    assert(512 ^^ x1 == 512);
+    assert(512 ^^ x3 == 0x8000000);
+    assert(1024 ^^ x0 == 1);
+    assert(1024 ^^ x1 == 1024);
+    assert(1024 ^^ x3 == 0x40000000);
+    assert(2048 ^^ x0 == 1);
+    assert(2048 ^^ x1 == 2048);
+    assert(2048 ^^ x2 == 0x400000);
+    assert(4096 ^^ x0 == 1);
+    assert(4096 ^^ x1 == 4096);
+    assert(4096 ^^ x2 == 0x1000000);
+    assert(8192 ^^ x0 == 1);
+    assert(8192 ^^ x1 == 8192);
+    assert(8192 ^^ x2 == 0x4000000);
+    assert(16384 ^^ x0 == 1);
+    assert(16384 ^^ x1 == 16384);
+    assert(16384 ^^ x2 == 0x10000000);
+    assert(32768 ^^ x0 == 1);
+    assert(32768 ^^ x1 == 32768);
+    assert(32768 ^^ x2 == 0x40000000);
+    assert(65536 ^^ x0 == 1);
+    assert(65536 ^^ x1 == 65536);
+    assert(131072 ^^ x0 == 1);
+    assert(131072 ^^ x1 == 131072);
+    assert(262144 ^^ x0 == 1);
+    assert(262144 ^^ x1 == 262144);
+    assert(524288 ^^ x0 == 1);
+    assert(524288 ^^ x1 == 524288);
+    assert(1048576 ^^ x0 == 1);
+    assert(1048576 ^^ x1 == 1048576);
+    assert(2097152 ^^ x0 == 1);
+    assert(2097152 ^^ x1 == 2097152);
+    assert(4194304 ^^ x0 == 1);
+    assert(4194304 ^^ x1 == 4194304);
 }
 
-static assert(magicVariable()==3);
-
-/************************************/
 // https://issues.dlang.org/show_bug.cgi?id=11159
 
 void test11159()
@@ -27,13 +98,7 @@ void test11159()
     assert(e_10_pow_20 == pow(10uL, 20));
 }
 
-// https://issues.dlang.org/show_bug.cgi?id=991 -- invalid.
-// https://issues.dlang.org/show_bug.cgi?id=3500 -- is this related to 2127?
-
-// Tests for ^^
-// TODO: These tests should not require import std.math.
-
-import std.math;
+// CTFE / typing rules for `^^`
 // Test float ^^ int
 static assert( 27.0 ^^ 5 == 27.0 * 27.0 * 27.0 * 27.0 * 27.0);
 static assert( 2.0 ^^ 3 == 8.0);
@@ -153,14 +218,6 @@ int containsAsm()
     return 0;
 }
 
-enum A = StructWithCtor(1);
-enum B = StructWithCtor(7, 2.3);
-
-static assert(A.n == 1);
-static assert(A.x == 5.0);
-static assert(B.n == 7);
-static assert(B.x == 2.3);
-
 int bazra(int x)
 {
    StructWithCtor p = StructWithCtor(4);
@@ -177,82 +234,6 @@ void moreCommaTests()
    for (int i=0; i< k^^2; i+=StructWithCtor(1).n) {}
 }
 
-// Test copy constructors
-struct CopyTest {
-   double x;
-   this(double a) { x = a * 10.0;}
-   this(this) {  x+=2.0;}
-}
-
-struct CopyTest2
-{
-   int x; int x1; int x2; int x3;
-   this(int a) { x = a * 2; x1 = 3;}
-   this(this) {  x1+=17;}
-}
-
-
-const CopyTest z = CopyTest(5.3);
-/+
-// TODO: This is not yet supported. But it
-// generates an error message instead of wrong-code.
-const CopyTest w = z;
-static assert(z.x==55.0);
-+/
-
-int copytest1()
-{
-   CopyTest z = CopyTest(3.4);
-   CopyTest w = z;
-   assert(w.x == 36.0);
-   CopyTest2 q = CopyTest2(7);
-   CopyTest2 q2 = q;
-   CopyTest2 q3 = q2;
-   assert(q3.x1 == 37);
-
-  return 123;
-}
-static assert(copytest1()==123);
-
-// This must not cause a segfault
-alias int FILTH;
-struct Filth
-{
-     struct Impl
-    {
-        FILTH * handle = null;
-        this(FILTH* h, uint r, string n)
-        {
-            handle = h;
-        }
-    }
-    Impl * p;
-
-    this(string name, in char[] stdioOpenmode = "rb")
-    {
-    }
-
-    ~this()
-    {
-        if (!p) return;
-    }
-
-    this(this)
-    {
-        if (!p) return;
-    }
-    }
-    struct InputByChar
-    {
-        private Filth _f;
-
-        this(Filth f)
-        {
-            _f = f;
-        }
-}
-
-
 static int nastyForCtfe=4;
 
 // Can't use a global variable
@@ -264,11 +245,8 @@ int anotherPowTest()
    return x^^4 > 2.0 ? 3: 2;
 }
 
-/************************************/
-
 // https://github.com/dlang/dmd/issues/19075
 // ^^= must compile for small integer types
-
 void test19075()
 {
     byte bw = 10;
@@ -288,12 +266,71 @@ void test19075()
     assert(usw == cast(ushort) 1_000_000);
 }
 
+/************************************/
+// https://issues.dlang.org/show_bug.cgi?id=3841
+// `^^=` must compile for the type combinations below
+
+void powAssign(LHS, RHS)()
+{
+    LHS a;
+    RHS b;
+    a ^^= b;
+}
+
+void testPowAssign()
+{
+    powAssign!(int, int)();
+    powAssign!(long, int)();
+    powAssign!(long, short)();
+    powAssign!(float, long)();
+    powAssign!(double, float)();
+    powAssign!(float, double)();
+}
+
+// https://issues.dlang.org/show_bug.cgi?id=4465
+void bug4465()
+{
+    const a = 2 ^^ 2;
+    int b = a;
+}
+
+// https://issues.dlang.org/show_bug.cgi?id=6228
+void test6228()
+{
+    int val;
+    const(int)* ptr = &val;
+    const(int)  temp;
+    auto x = (*ptr) ^^ temp;
+}
+
+// https://issues.dlang.org/show_bug.cgi?id=10682
+void text10682()
+{
+    ulong x = 1;
+    ulong y = 2 ^^ x;
+}
+
+// https://issues.dlang.org/show_bug.cgi?id=14166
+struct S14166
+{
+    int x;
+    double y;
+}
+S14166 s14166;
+
+static assert(is(typeof(s14166.x ^^ 2) == int));
+static assert(is(typeof(s14166.y ^^= 2.5) == double));
+
 /************************************/
 
 void main()
 {
-    assert(!__ctfe);
-    assert(magicVariable()==2);
+    test5943();
     test11159();
     test19075();
+    testPowAssign();
+    moreCommaTests();
+    bug4465();
+    test6228();
+    text10682();
 }
diff --git a/compiler/test/runnable/test13117.d b/compiler/test/runnable/test13117.d
index 06563b8d1226..65c99b17d733 100644
--- a/compiler/test/runnable/test13117.d
+++ b/compiler/test/runnable/test13117.d
@@ -1,4 +1,5 @@
 // PERMUTE_ARGS: -O -release -g
+// RUNNABLE_PHOBOS_TEST
 import std.file, std.stdio;
 
 int main()
diff --git a/compiler/test/runnable/test13117b.d b/compiler/test/runnable/test13117b.d
index d14bd595c339..dd59f29523f6 100644
--- a/compiler/test/runnable/test13117b.d
+++ b/compiler/test/runnable/test13117b.d
@@ -1,5 +1,6 @@
 // REQUIRED_ARGS: -inline
 // PERMUTE_ARGS: -O -release -g
+// RUNNABLE_PHOBOS_TEST
 import std.file, std.stdio;
 
 int main()
diff --git a/compiler/test/runnable/test18076.sh b/compiler/test/runnable/test18076.sh
index f4622e5658fb..a8cf27aa9a0f 100755
--- a/compiler/test/runnable/test18076.sh
+++ b/compiler/test/runnable/test18076.sh
@@ -2,7 +2,7 @@
 
 output_file=${OUTPUT_BASE}.log
 
-echo 'import std.stdio; void main() { writeln("Success"); }' | \
+echo 'import core.stdc.stdio; void main() { puts("Success"); }' | \
 	$DMD -m${MODEL} -run - > ${output_file}
 grep -q 'Success' ${output_file}
 
diff --git a/compiler/test/runnable/test19.d b/compiler/test/runnable/test19.d
index eda6172abc04..d0d4db1d8188 100644
--- a/compiler/test/runnable/test19.d
+++ b/compiler/test/runnable/test19.d
@@ -1,7 +1,5 @@
 // REQUIRED_ARGS: -unittest
 
-import std.algorithm: cmp;
-
 extern(C) int printf(const char*, ...);
 
 /* ================================ */
@@ -269,7 +267,7 @@ void test13()
 
     s1 = s1.dup;
     s2 = tolower13(s1);
-    assert(cmp(s2, "fol") == 0);
+    assert(s2 == "fol");
     assert(s2 == s1);
 }
 
diff --git a/compiler/test/runnable/test5943.d b/compiler/test/runnable/test5943.d
deleted file mode 100644
index 0d6619872d78..000000000000
--- a/compiler/test/runnable/test5943.d
+++ /dev/null
@@ -1,77 +0,0 @@
-// test that the import of std.math is not needed
-
-__gshared uint x0 = 0;
-__gshared uint x1 = 1;
-__gshared uint x2 = 2;
-__gshared uint x3 = 3;
-__gshared uint x4 = 4;
-__gshared uint x5 = 5;
-__gshared uint x6 = 6;
-__gshared uint x7 = 7;
-__gshared uint x10 = 10;
-__gshared uint x15 = 15;
-__gshared uint x31 = 31;
-__gshared uint x32 = 32;
-
-void main()
-{
-    assert(2 ^^ x0 == 1);
-    assert(2 ^^ x1 == 2);
-    assert(2 ^^ x31 == 0x80000000);
-    assert(4 ^^ x0 == 1);
-    assert(4 ^^ x1 == 4);
-    assert(4 ^^ x15 == 0x40000000);
-    assert(8 ^^ x0 == 1);
-    assert(8 ^^ x1 == 8);
-    assert(8 ^^ x10 == 0x40000000);
-    assert(16 ^^ x0 == 1);
-    assert(16 ^^ x1 == 16);
-    assert(16 ^^ x7 == 0x10000000);
-    assert(32 ^^ x0 == 1);
-    assert(32 ^^ x1 == 32);
-    assert(32 ^^ x6 == 0x40000000);
-    assert(64 ^^ x0 == 1);
-    assert(64 ^^ x1 == 64);
-    assert(64 ^^ x5 == 0x40000000);
-    assert(128 ^^ x0 == 1);
-    assert(128 ^^ x1 == 128);
-    assert(128 ^^ x4 == 0x10000000);
-    assert(256 ^^ x0 == 1);
-    assert(256 ^^ x1 == 256);
-    assert(256 ^^ x3 == 0x1000000);
-    assert(512 ^^ x0 == 1);
-    assert(512 ^^ x1 == 512);
-    assert(512 ^^ x3 == 0x8000000);
-    assert(1024 ^^ x0 == 1);
-    assert(1024 ^^ x1 == 1024);
-    assert(1024 ^^ x3 == 0x40000000);
-    assert(2048 ^^ x0 == 1);
-    assert(2048 ^^ x1 == 2048);
-    assert(2048 ^^ x2 == 0x400000);
-    assert(4096 ^^ x0 == 1);
-    assert(4096 ^^ x1 == 4096);
-    assert(4096 ^^ x2 == 0x1000000);
-    assert(8192 ^^ x0 == 1);
-    assert(8192 ^^ x1 == 8192);
-    assert(8192 ^^ x2 == 0x4000000);
-    assert(16384 ^^ x0 == 1);
-    assert(16384 ^^ x1 == 16384);
-    assert(16384 ^^ x2 == 0x10000000);
-    assert(32768 ^^ x0 == 1);
-    assert(32768 ^^ x1 == 32768);
-    assert(32768 ^^ x2 == 0x40000000);
-    assert(65536 ^^ x0 == 1);
-    assert(65536 ^^ x1 == 65536);
-    assert(131072 ^^ x0 == 1);
-    assert(131072 ^^ x1 == 131072);
-    assert(262144 ^^ x0 == 1);
-    assert(262144 ^^ x1 == 262144);
-    assert(524288 ^^ x0 == 1);
-    assert(524288 ^^ x1 == 524288);
-    assert(1048576 ^^ x0 == 1);
-    assert(1048576 ^^ x1 == 1048576);
-    assert(2097152 ^^ x0 == 1);
-    assert(2097152 ^^ x1 == 2097152);
-    assert(4194304 ^^ x0 == 1);
-    assert(4194304 ^^ x1 == 4194304);
-}
diff --git a/compiler/test/runnable/test8544.d b/compiler/test/runnable/test8544.d
index 0b8b86bd99fc..6d92270e834a 100644
--- a/compiler/test/runnable/test8544.d
+++ b/compiler/test/runnable/test8544.d
@@ -1,7 +1,6 @@
 // EXECUTE_ARGS: foo bar doo
 // PERMUTE_ARGS:
-import core.stdc.stdio;
-import std.conv;
+import core.stdc.string : strlen;
 import core.runtime;
 
 void main(string[] args)
@@ -12,6 +11,7 @@ void main(string[] args)
     assert(dArgs.length && cArgs.argc);  // ensure we've passed some args
     assert(dArgs.length == cArgs.argc);
 
-    assert(dArgs[1] == to!string(cArgs.argv[1]));
-    assert(args[1] == to!string(cArgs.argv[1]));
+    const cArg = cArgs.argv[1][0 .. strlen(cArgs.argv[1])];
+    assert(dArgs[1] == cArg);
+    assert(args[1] == cArg);
 }
diff --git a/compiler/test/runnable/test9287.sh b/compiler/test/runnable/test9287.sh
index bcee882c2c35..245690ad0653 100755
--- a/compiler/test/runnable/test9287.sh
+++ b/compiler/test/runnable/test9287.sh
@@ -2,7 +2,7 @@
 
 set -e
 
-echo 'import std.stdio; void main() { writeln("Success"); }' | \
+echo 'import core.stdc.stdio; void main() { puts("Success"); }' | \
 	$DMD -m${MODEL} -of${OUTPUT_BASE}${EXE} -
 
 ${OUTPUT_BASE}${EXE}
diff --git a/compiler/test/runnable/testabi.d b/compiler/test/runnable/testabi.d
index d84cf4f499d6..9f014af259f9 100644
--- a/compiler/test/runnable/testabi.d
+++ b/compiler/test/runnable/testabi.d
@@ -782,7 +782,7 @@ ulong mask(ulong n)
 {
         if ( n == ulong.sizeof )   // may wrap
                 return ~0UL;
-        return 2^^( n*8 ) - 1;
+        return (1UL << (n*8)) - 1;
 }
 
 /************************************************************************/
diff --git a/compiler/test/runnable/xtest46.d b/compiler/test/runnable/xtest46.d
index 5893560a6226..af0ed3c48b06 100644
--- a/compiler/test/runnable/xtest46.d
+++ b/compiler/test/runnable/xtest46.d
@@ -888,14 +888,6 @@ void test45()
 
 /***************************************************/
 
-void text10682()
-{
-    ulong x = 1;
-    ulong y = 2 ^^ x;
-}
-
-/***************************************************/
-
 struct Test46
 {
  int foo;
@@ -2453,14 +2445,6 @@ void test118() {}
 
 /***************************************************/
 
-void bug4465()
-{
-    const a = 2 ^^ 2;
-    int b = a;
-}
-
-/***************************************************/
-
 pure void foo(int *p)
 {
     *p = 3;
@@ -4231,17 +4215,6 @@ void test1962()
     assert(C.classinfo.create() is null);
 }
 
-/***************************************************/
-// https://issues.dlang.org/show_bug.cgi?id=6228
-
-void test6228()
-{
-    int val;
-    const(int)* ptr = &val;
-    const(int)  temp;
-    auto x = (*ptr) ^^ temp;
-}
-
 /***************************************************/
 
 int test7544()
@@ -8253,7 +8226,6 @@ int main()
     test1471();
     test6335();
     test1687();
-    test6228();
     test3733();
     test4392();
     test7942();
diff --git a/compiler/test/tools/d_do_test.d b/compiler/test/tools/d_do_test.d
index 9a17a4359a69..655df062ef07 100755
--- a/compiler/test/tools/d_do_test.d
+++ b/compiler/test/tools/d_do_test.d
@@ -93,6 +93,7 @@ struct TestArgs
     bool     compileSeparately;     /// `COMPILE_SEPARATELY`: compile each source file separately
     bool     link;                  /// `LINK`: force linking for `fail_compilation` & `compilable` tests
     bool     clearDflags;           /// `DFLAGS`: whether DFLAGS should be cleared before invoking dmd
+    bool     requirePhobos;         /// `RUNNABLE_PHOBOS_TEST`/`COMPILABLE_MATH_TEST`: test genuinely needs Phobos, so use it instead of druntime-only
     string   executeArgs;           /// `EXECUTE_ARGS`: arguments passed to the compiled executable (for `runnable[_cxx]`)
     string   cxxflags;              /// `CXXFLAGS`: arguments passed to $CXX when compiling `EXTRA_CPP_SOURCES`
     string[] sources;               /// `EXTRA_SOURCES`: additional D sources (+ main source file)
@@ -124,6 +125,8 @@ struct EnvData
 {
     string all_args;             /// `ARGS`: arguments to test in permutations
     string dmd;                  /// `DMD`: compiler under test
+    string hostDmd;              /// `HOST_DMD`: host compiler, used to build test-harness code (e.g. dshell scripts)
+    string phobosDflags;         /// `PHOBOS_DFLAGS`: Phobos-based `DFLAGS` for dshell tests and `RUNNABLE_PHOBOS_TEST` opt-in tests
     string results_dir;          /// `RESULTS_DIR`: directory for temporary files
     string sep;                  /// `SEP`: directory separator (`/` or `\`)
     string dsep;                 /// `DSEP`: double directory separator ( `/` or `\\`)
@@ -171,6 +174,8 @@ immutable(EnvData) processEnvironment()
     envData.exe            = envGetRequired ("EXE");
     envData.os             = environment.get("OS");
     envData.dmd            = replace(envGetRequired("DMD"), "/", envData.sep);
+    envData.hostDmd        = replace(environment.get("HOST_DMD", "dmd"), "/", envData.sep);
+    envData.phobosDflags   = environment.get("PHOBOS_DFLAGS", "");
     envData.compiler       = "dmd"; //should be replaced for other compilers
     envData.ccompiler      = environment.get("CC");
     envData.cxxcompiler    = environment.get("CXX");
@@ -658,6 +663,10 @@ bool gatherTestParameters(ref TestArgs testArgs, string input_dir, string input_
     testArgs.clearDflags = findTestParameter(envData, file, "DFLAGS", dflagsStr);
     enforce(dflagsStr.empty, "The DFLAGS test argument must be empty: It is '" ~ dflagsStr ~ "'");
 
+    // Tests are compiled/linked against druntime only; the rare test for which
+    // Phobos is essential opts in with one of these markers and gets Phobos.
+    testArgs.requirePhobos = file.canFind("RUNNABLE_PHOBOS_TEST") || file.canFind("COMPILABLE_MATH_TEST");
+
     findTestParameter(envData, file, "REQUIRED_ARGS", testArgs.requiredArgs);
     if (envData.required_args.length)
     {
@@ -1722,6 +1731,8 @@ int tryMain(string[] args)
     // Clear the DFLAGS environment variable if it was specified in the test file
     if (testArgs.clearDflags)
         environment["DFLAGS"] = "";
+    else if (testArgs.requirePhobos)
+        environment["DFLAGS"] = envData.phobosDflags;
 
     writef(" ... %-30s %s%s(%s)",
             input_file,
@@ -2344,11 +2355,15 @@ static this()
     auto outfile = File(output_file, "w");
     enum keepFilesOpen = Config.retainStdout | Config.retainStderr;
 
+    // dshell scripts are test-harness code that should not be driven by the
+    // compiler under test, but by a stable host compiler.
+    environment["DFLAGS"] = envData.phobosDflags;
+
     //
     // compile the test
     //
     {
-        const compile = [envData.dmd, "-conf=", "-m"~envData.model] ~
+        const compile = [envData.hostDmd, "-m"~envData.model] ~
             envData.picFlag ~ [
             "-od" ~ testOutDir,
             "-of" ~ testScriptExe,
@@ -2362,9 +2377,13 @@ static this()
         ];
         outfile.writeln("[COMPILE_TEST] ", escapeShellCommand(compile));
         outfile.flush();
+        // Build with the host compiler's own configuration: clear DFLAGS so the
+        // druntime-only flags (and the Phobos PHOBOS_DFLAGS) don't leak in here.
+        auto compileEnv = environment.toAA();
+        compileEnv.remove("DFLAGS");
         // Note that spawnprocess closes the file, so it will need to be re-opened
         // below when we run the test
-        auto compileProc = std.process.spawnProcess(compile, stdin, outfile, outfile, null, keepFilesOpen);
+        auto compileProc = std.process.spawnProcess(compile, stdin, outfile, outfile, compileEnv, keepFilesOpen);
         const exitCode = wait(compileProc);
         if (exitCode != 0)
         {

From 390d6b1a2f7195fa86ad5142690c6b89f04eeae1 Mon Sep 17 00:00:00 2001
From: Dennis Korpel <dkorpel@gmail.com>
Date: Wed, 3 Jun 2026 12:58:12 +0200
Subject: [PATCH 2/7] test6716.d: link druntime instead of phobos

---
 compiler/test/runnable_cxx/test6716.d | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/compiler/test/runnable_cxx/test6716.d b/compiler/test/runnable_cxx/test6716.d
index 6aeb25d6dcca..4cf6df8cadb0 100644
--- a/compiler/test/runnable_cxx/test6716.d
+++ b/compiler/test/runnable_cxx/test6716.d
@@ -4,13 +4,7 @@ version(Windows)
 {
     // without main, there is no implicit reference to the runtime library
     // other platforms pass the runtime library on the linker command line
-    version(CRuntime_Microsoft)
-        version(Win64)
-            pragma(lib, "phobos64");
-        else
-            pragma(lib, "phobos32mscoff");
-    else
-        pragma(lib, "phobos");
+    pragma(lib, "druntime");
 }
 
 extern(C++) int test6716(int magic)

From 2a563b1e6f913e3676f4c7c83c58dda4148c2e09 Mon Sep 17 00:00:00 2001
From: Dennis Korpel <dkorpel@gmail.com>
Date: Wed, 3 Jun 2026 13:15:01 +0200
Subject: [PATCH 3/7] Pass absolute HOST_DMD path

---
 ci/run.sh           | 2 +-
 compiler/test/run.d | 5 ++++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/ci/run.sh b/ci/run.sh
index 77b2d88bc948..2956e64817f1 100755
--- a/ci/run.sh
+++ b/ci/run.sh
@@ -128,7 +128,7 @@ test_dmd() {
     fi
 
     $build_path/dmd -g -i -Icompiler/test -release compiler/test/run.d -ofgenerated/run
-    generated/run -j$N --environment MODEL=$MODEL HOST_DMD=$build_path/dmd "${args[@]}"
+    generated/run -j$N --environment MODEL=$MODEL HOST_DMD="$PWD/$build_path/dmd" "${args[@]}"
 }
 
 # build and run druntime unit tests
diff --git a/compiler/test/run.d b/compiler/test/run.d
index f59fa7b3b3f8..c66657e40cda 100755
--- a/compiler/test/run.d
+++ b/compiler/test/run.d
@@ -128,6 +128,9 @@ Options:
     }
 
     // allow overwrites from the environment
+    // HOST_DMD must be either a command on PATH (e.g. `dmd`, `ldmd2`) or an
+    // absolute path; it is used to build test-harness code (dshell scripts,
+    // tools) which runs from various working directories.
     hostDMD = environment.get("HOST_DMD", "dmd");
     unitTestRunnerCommand = resultsDir.buildPath("unit_test_runner").exeName;
 
@@ -584,7 +587,7 @@ string[string] getEnvironment()
         env["DSEP"] = `\\`;
         env["SEP"] = `\`;
         env["DFLAGS"] = `-I"%s\import" -defaultlib=druntime -debuglib=druntime`.format(druntimePath);
-        env["LIB"] = druntimeLibDir ~ ";" ~ environment.get("LIB");
+        env["LIB"] = druntimeLibDir ~ ";" ~ phobosPath ~ ";" ~ environment.get("LIB");
         env["PHOBOS_DFLAGS"] = `-I"%s\import" -I"%s"`.format(druntimePath, phobosPath);
     }
     else

From 7821338c8a38f4116e7fe9ee38375b63cf22fae7 Mon Sep 17 00:00:00 2001
From: Dennis Korpel <dkorpel@gmail.com>
Date: Wed, 3 Jun 2026 17:09:36 +0200
Subject: [PATCH 4/7] test runner: map BUILD config to a valid druntime build
 flavor

VisualD passes the dmd build configuration (e.g. Debug, RelWithAsserts)
as BUILD, but the druntime/phobos makefiles only accept debug or release.
ensureDruntime then failed with "Unrecognized BUILD=Debug". Normalize the
runtime library flavor independently from the compiler configuration.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 compiler/test/run.d | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/compiler/test/run.d b/compiler/test/run.d
index c66657e40cda..b743e0831a86 100755
--- a/compiler/test/run.d
+++ b/compiler/test/run.d
@@ -231,6 +231,20 @@ void verifyCompilerExists(const string[string] env)
     }
 }
 
+/**
+Maps the test runner's `BUILD` to a runtime library build flavor.
+
+`BUILD` may be a dmd build configuration that only describes the compiler
+binary (e.g. VisualD passes `Debug` or `RelWithAsserts`), whereas the
+druntime/phobos makefiles only accept `debug` or `release`. The runtime
+library flavor is independent from the compiler's configuration, so anything
+that isn't explicitly a debug build maps to `release`.
+*/
+string runtimeBuild(string build)
+{
+    return build.toLower == "debug" ? "debug" : "release";
+}
+
 /**
 Builds (or rebuilds) the druntime library that the tests link against.
 
@@ -243,7 +257,7 @@ void ensureDruntime(const string[string] env)
     const buildCommand = [
         make, "-C", druntimeDir,
         "MODEL=" ~ env["MODEL"],
-        "BUILD=" ~ env["BUILD"],
+        "BUILD=" ~ runtimeBuild(env["BUILD"]),
     ];
 
     writefln("Building druntime: %-(%s %)", buildCommand);
@@ -576,7 +590,7 @@ string[string] getEnvironment()
     const generatedSuffix = "generated/%s/%s/%s".format(os, build, model);
 
     const druntimePath = environment.get("DRUNTIME_PATH", projectRootDir.buildPath("druntime"));
-    const druntimeLibDir = generatedDir.buildPath(os, build, model);
+    const druntimeLibDir = generatedDir.buildPath(os, runtimeBuild(build), model);
 
     const phobosPath = environment.get("PHOBOS_PATH", projectRootDir.dirName.buildPath("phobos"));
 

From 8fd6a10de14ca56c3087f990e0e4f10fe46248c7 Mon Sep 17 00:00:00 2001
From: Dennis Korpel <dkorpel@gmail.com>
Date: Fri, 5 Jun 2026 13:00:36 +0200
Subject: [PATCH 5/7] test runner: pass DMD to druntime build so it isn't
 rebuilt

ensureDruntime invoked the druntime Makefile without DMD=, so its default
DMD path (generated/<os>/<build>/<model>/dmd) pointed at a nonexistent
binary on the VisualD CI (dmd lives under RelWithAsserts/), triggering a
"make -C .. dmd" that failed compiling build.d against absent Phobos.
Pass the existing compiler explicitly.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 compiler/test/run.d | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/compiler/test/run.d b/compiler/test/run.d
index b743e0831a86..150cc0a2161b 100755
--- a/compiler/test/run.d
+++ b/compiler/test/run.d
@@ -258,6 +258,10 @@ void ensureDruntime(const string[string] env)
         make, "-C", druntimeDir,
         "MODEL=" ~ env["MODEL"],
         "BUILD=" ~ runtimeBuild(env["BUILD"]),
+        // Pass the existing compiler so the druntime Makefile doesn't try to
+        // (re)build dmd itself, which fails when the compiler lives in a
+        // different generated/ subdirectory (e.g. VisualD's RelWithAsserts).
+        "DMD=" ~ env["DMD"],
     ];
 
     writefln("Building druntime: %-(%s %)", buildCommand);

From 944bfba01d56fa495f82f035802883c7c4bb9b2a Mon Sep 17 00:00:00 2001
From: Dennis Korpel <dkorpel@gmail.com>
Date: Fri, 12 Jun 2026 11:53:56 +0200
Subject: [PATCH 6/7] test runner: build dshell harness with compiler under
 test

The dshell prebuilt library and per-test driver were built with the host
compiler (e.g. LDC 1.23 on the VisualD CI), which is too old to parse the
current druntime/Phobos sources (short '=>' function bodies etc.), causing
parse errors when their imports were analyzed. They also import Phobos and
link against each other, so build both with the compiler under test using
PHOBOS_DFLAGS instead, matching the pre-druntime-only behaviour.

Also strip the benign LNK4255 'multiple objects of the same name' linker
warning: druntime.lib is built as one 'dmd -lib' archive and contains
several objects sharing a basename (memory.obj etc.), so the MS linker
warns when linking with -g, leaking into tests that expect no output.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 compiler/test/run.d             | 12 ++++++++++--
 compiler/test/tools/d_do_test.d | 21 +++++++++++++--------
 2 files changed, 23 insertions(+), 10 deletions(-)

diff --git a/compiler/test/run.d b/compiler/test/run.d
index 150cc0a2161b..8fc386b5e542 100755
--- a/compiler/test/run.d
+++ b/compiler/test/run.d
@@ -337,15 +337,23 @@ void ensureToolsExists(const string[string] env, const TestTool[] tools ...)
         }
 
         string[] buildCommand;
+        string[string] buildEnv = null;
         if (tool.linksWithTests)
         {
+            // The dshell library imports Phobos and is linked against the tests,
+            // so it must be built by the compiler under test (the host compiler
+            // may be too old to parse the current druntime/Phobos) using the
+            // Phobos DFLAGS rather than the druntime-only default.
             buildCommand = [
-                hostDMD,
+                env["DMD"],
+                "-conf=",
                 "-m"~env["MODEL"],
                 "-of" ~ targetBin,
                 "-c",
                 sourceFile
             ] ~ getPicFlags(env);
+            buildEnv = env.dup;
+            buildEnv["DFLAGS"] = env.get("PHOBOS_DFLAGS", "");
         }
         else
         {
@@ -359,7 +367,7 @@ void ensureToolsExists(const string[string] env, const TestTool[] tools ...)
 
         writefln("Executing: %-(%s %)", buildCommand);
         stdout.flush();
-        if (spawnProcess(buildCommand, null).wait)
+        if (spawnProcess(buildCommand, buildEnv).wait)
         {
             stderr.writefln("failed to build '%s'", targetBin);
             atomicOp!"+="(failCount, 1);
diff --git a/compiler/test/tools/d_do_test.d b/compiler/test/tools/d_do_test.d
index 655df062ef07..6ac5a67ce0b5 100755
--- a/compiler/test/tools/d_do_test.d
+++ b/compiler/test/tools/d_do_test.d
@@ -1845,6 +1845,12 @@ int tryMain(string[] args)
 
                 compile_output = compile_output.unifyNewLine();
                 compile_output = std.regex.replaceAll(compile_output, regex(`^DMD v2\.[0-9]+.*\n? DEBUG$`, "m"), "");
+                // druntime.lib is built as a single library with `dmd -lib`, so
+                // it contains several object files with the same basename (e.g.
+                // memory.obj from core.memory and rt.memory). The MS linker emits
+                // a benign LNK4255 warning about this when linking with `-g`;
+                // strip it so it doesn't fail tests that expect no output.
+                compile_output = std.regex.replaceAll(compile_output, regex(`^.*warning LNK4255:.*\n?`, "m"), "");
                 compile_output = std.string.strip(compile_output);
                 // replace test_result path with fixed ones
                 compile_output = compile_output.replace(result_path, resultsDirReplacement);
@@ -2355,15 +2361,18 @@ static this()
     auto outfile = File(output_file, "w");
     enum keepFilesOpen = Config.retainStdout | Config.retainStderr;
 
-    // dshell scripts are test-harness code that should not be driven by the
-    // compiler under test, but by a stable host compiler.
+    // dshell scripts import Phobos (std.process etc.) and link against the
+    // prebuilt dshell library, so build them with the compiler under test and
+    // the Phobos DFLAGS: the host compiler may be too old to parse the current
+    // druntime/Phobos sources, and the prebuilt library is built by the
+    // compiler under test too, so both must agree.
     environment["DFLAGS"] = envData.phobosDflags;
 
     //
     // compile the test
     //
     {
-        const compile = [envData.hostDmd, "-m"~envData.model] ~
+        const compile = [envData.dmd, "-conf=", "-m"~envData.model] ~
             envData.picFlag ~ [
             "-od" ~ testOutDir,
             "-of" ~ testScriptExe,
@@ -2377,13 +2386,9 @@ static this()
         ];
         outfile.writeln("[COMPILE_TEST] ", escapeShellCommand(compile));
         outfile.flush();
-        // Build with the host compiler's own configuration: clear DFLAGS so the
-        // druntime-only flags (and the Phobos PHOBOS_DFLAGS) don't leak in here.
-        auto compileEnv = environment.toAA();
-        compileEnv.remove("DFLAGS");
         // Note that spawnprocess closes the file, so it will need to be re-opened
         // below when we run the test
-        auto compileProc = std.process.spawnProcess(compile, stdin, outfile, outfile, compileEnv, keepFilesOpen);
+        auto compileProc = std.process.spawnProcess(compile, stdin, outfile, outfile, null, keepFilesOpen);
         const exitCode = wait(compileProc);
         if (exitCode != 0)
         {

From e35773ca1d32296aca67624907e21e98023d84cc Mon Sep 17 00:00:00 2001
From: Dennis Korpel <dkorpel@gmail.com>
Date: Sat, 13 Jun 2026 20:27:04 +0200
Subject: [PATCH 7/7] test runner: fix const AA copy for dshell build env

`const(string)[string].dup` yields `const(string)[string]`, which doesn't
implicitly convert to the mutable `string[string]` spawnProcess wants. Copy
the entries into a mutable AA explicitly instead.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 compiler/test/run.d | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/compiler/test/run.d b/compiler/test/run.d
index 8fc386b5e542..5122fb4e0b40 100755
--- a/compiler/test/run.d
+++ b/compiler/test/run.d
@@ -352,7 +352,8 @@ void ensureToolsExists(const string[string] env, const TestTool[] tools ...)
                 "-c",
                 sourceFile
             ] ~ getPicFlags(env);
-            buildEnv = env.dup;
+            foreach (k, v; env)
+                buildEnv[k] = v;
             buildEnv["DFLAGS"] = env.get("PHOBOS_DFLAGS", "");
         }
         else