From a43cdf42f46bfc6262052af97dc310596b0c6dc8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?D=C4=81vis=20Mos=C4=81ns?= <davispuh@gmail.com>
Date: Wed, 11 Mar 2026 22:15:10 +0200
Subject: [PATCH] Comment out compiler builtins

Consider C header like:
```
 #define va_copy __builtin_va_copy
 #define ALIGNOF(TYPE)  _Alignof (TYPE)
 #define __unused  __attribute__((__unused__))
 #define __noreturn  __attribute__((__noreturn__))
 #define STATIC_ASSERT  _Static_assert
 #define CONST  const
 #define STATIC  static
 #define __volatile  volatile
```

This commit implements commenting out such compiler builtins with `// FIXME:` prefix.
---
 dstep/translator/MacroDefinition.d | 26 ++++++++++++++++++++++----
 tests/unit/MacroTranslTests.d      | 22 ++++++++++++++++++++++
 2 files changed, 44 insertions(+), 4 deletions(-)

diff --git a/dstep/translator/MacroDefinition.d b/dstep/translator/MacroDefinition.d
index 1775c982..cebcea68 100644
--- a/dstep/translator/MacroDefinition.d
+++ b/dstep/translator/MacroDefinition.d
@@ -522,6 +522,7 @@ bool translateFunctAlias(
 {
     import std.algorithm.comparison : equal;
     import std.algorithm.iteration : map;
+    import std.algorithm.searching : startsWith;
 
     CallExpr* expr = definition.expr.peek!CallExpr;
     auto expressionContext = ExpressionContext.make(context);
@@ -554,11 +555,17 @@ bool translateFunctAlias(
                 .map!(a => a.translate(expressionContext))))
         {
             version (D1)
-                enum fmt = "alias %2$s %1$s;";
+                string fmt = "alias %2$s %1$s;";
             else
-                enum fmt = "alias %1$s = %2$s;";
+                string fmt = "alias %1$s = %2$s;";
 
-            output.singleLine(fmt, definition.spelling, ident.spelling);
+            // Handle compiler builtins (eg. __builtin_unreachable)
+            string value = ident.spelling;
+            if (value.startsWith("__builtin_") || value == "_Alignof")
+            {
+                fmt = "// FIXME: " ~ fmt;
+            }
+            output.singleLine(fmt, definition.spelling, value);
             return true;
         }
     }
@@ -592,6 +599,8 @@ void translateMacroDefinitionAliasOrConst(
     Context context,
     TypedMacroDefinition definition)
 {
+    import std.algorithm.searching : startsWith, canFind;
+
     auto expressionContext = ExpressionContext.make(context);
 
     string formatString;
@@ -612,10 +621,19 @@ void translateMacroDefinitionAliasOrConst(
             formatString = "enum %s = %s;";
     }
 
+    string value = debraced.translate(expressionContext);
+    if (["const", "static", "volatile", "_Static_assert"].canFind(value) ||
+        // Handle compiler builtins
+        value.startsWith("__builtin_") ||
+        value.startsWith("__attribute__"))
+    {
+        formatString = "// FIXME: " ~ formatString;
+    }
+
     output.singleLine(
         formatString,
         definition.definition.spelling,
-        debraced.translate(expressionContext));
+        value);
 
     expressionContext.elevateImports();
 }
diff --git a/tests/unit/MacroTranslTests.d b/tests/unit/MacroTranslTests.d
index 6a7cb3c3..d95f524b 100644
--- a/tests/unit/MacroTranslTests.d
+++ b/tests/unit/MacroTranslTests.d
@@ -841,3 +841,25 @@ extern (D) auto fun(T)(auto ref T a)
 }
 D");
 }
+
+// Comment out compiler builtins and language keywords.
+unittest
+{
+    assertTMD(q"C
+#define va_copy __builtin_va_copy
+C", q"D
+// FIXME: enum va_copy = __builtin_va_copy;
+D");
+
+    assertTMD(q"C
+#define fake _builtin_fake
+C", q"D
+enum fake = _builtin_fake;
+D");
+
+    assertTMD(q"C
+#define foo(x) __builtin_foo(x)
+C", q"D
+// FIXME: alias foo = __builtin_foo;
+D");
+}