[PATCH] D72405: Allow /D flags absent during PCH creation under msvc-compat

[Reid Kleckner via Phabricator via cfe-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rG0f9cf42facaf: Allow /D flags absent during PCH creation under msvc-compat (authored by zahen, committed by rnk).

Changed prior to commit:
  https://reviews.llvm.org/D72405?vs=238147&id=238149#toc

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D72405/new/

https://reviews.llvm.org/D72405

Files:
  clang/lib/Lex/PPDirectives.cpp
  clang/test/PCH/ms-pch-macro.c


Index: clang/test/PCH/ms-pch-macro.c
===================================================================
--- /dev/null
+++ clang/test/PCH/ms-pch-macro.c
@@ -0,0 +1,39 @@
+// Test -D and -U interaction with a PCH when -fms-extensions is enabled.
+
+// RUN: %clang_cc1 -DFOO %S/variables.h -emit-pch -o %t1.pch
+
+// RUN: not %clang_cc1 -DFOO=blah -DBAR=int -include-pch %t1.pch -pch-through-header=%S/variables.h %s 2> %t.err
+// RUN: FileCheck -check-prefix=CHECK-FOO %s < %t.err
+
+// RUN: not %clang_cc1 -UFOO -DBAR=int -include-pch %t1.pch %s -pch-through-header=%S/variables.h 2> %t.err
+// RUN: FileCheck -check-prefix=CHECK-NOFOO %s < %t.err
+
+// RUN: %clang_cc1 -include-pch %t1.pch -DBAR=int -pch-through-header=%S/variables.h -verify %s 2> %t.err
+
+// Enabling MS extensions should allow us to add BAR definitions.
+// RUN: %clang_cc1 -fms-extensions -DFOO %S/variables.h -emit-pch -o %t1.pch
+// RUN: %clang_cc1 -fms-extensions -include-pch %t1.pch -DBAR=int -pch-through-header=%S/variables.h -verify %s 2> %t.err
+
+#include "variables.h"
+
+BAR bar = 17;
+#ifndef _MSC_EXTENSIONS
+// expected-error at -2 {{unknown type name 'BAR'}}
+#endif
+
+#ifndef FOO
+#  error FOO was not defined
+#endif
+
+#if FOO != 1
+#  error FOO has the wrong definition
+#endif
+
+#if defined(_MSC_EXTENSIONS) && !defined(BAR)
+#  error BAR was not defined
+#endif
+
+// CHECK-FOO: definition of macro 'FOO' differs between the precompiled header ('1') and the command line ('blah')
+// CHECK-NOFOO: macro 'FOO' was defined in the precompiled header but undef'd on the command line
+
+// expected-warning at 1 {{definition of macro 'BAR' does not match definition in precompiled header}}
Index: clang/lib/Lex/PPDirectives.cpp
===================================================================
--- clang/lib/Lex/PPDirectives.cpp
+++ clang/lib/Lex/PPDirectives.cpp
@@ -2727,7 +2727,9 @@
                              /*Syntactic=*/LangOpts.MicrosoftExt))
       Diag(MI->getDefinitionLoc(), diag::warn_pp_macro_def_mismatch_with_pch)
           << MacroNameTok.getIdentifierInfo();
-    return;
+    // Issue the diagnostic but allow the change if msvc extensions are enabled
+    if (!LangOpts.MicrosoftExt)
+      return;
   }
 
   // Finally, if this identifier already had a macro defined for it, verify that


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