Revert "[clang] Remove #undef alloca workaround"

[Prabhuk]

Reverts #81534

#81534 breaks building (Fuchsia) Clang toolchain on Windows.

Log: https://logs.chromium.org/logs/fuchsia/buildbucket/cr-buildbucket/8756186536543250705/+/u/clang/install/stdout
Builder: https://ci.chromium.org/ui/p/fuchsia/builders/toolchain.ci/clang-windows-x64/b8756186536543250705/overview

FAILED: tools/clang/tools/extra/clang-include-fixer/tool/CMakeFiles/clang-include-fixer.dir/ClangIncludeFixer.cpp.obj 
C:\b\s\w\ir\x\w\cipd\bin\clang-cl.exe  /nologo -TP -DCLANG_REPOSITORY_STRING=\"https://llvm.googlesource.com/llvm-project\" -DGTEST_HAS_RTTI=0 -DUNICODE -D_CRT_NONSTDC_NO_DEPRECATE -D_CRT_NONSTDC_NO_WARNINGS -D_CRT_SECURE_NO_DEPRECATE -D_CRT_SECURE_NO_WARNINGS -D_GLIBCXX_ASSERTIONS -D_HAS_EXCEPTIONS=0 -D_SCL_SECURE_NO_DEPRECATE -D_SCL_SECURE_NO_WARNINGS -D_UNICODE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -IC:\b\s\w\ir\x\w\llvm_build\tools\clang\tools\extra\clang-include-fixer\tool -IC:\b\s\w\ir\x\w\llvm-llvm-project\clang-tools-extra\clang-include-fixer\tool -IC:\b\s\w\ir\x\w\llvm-llvm-project\clang\include -IC:\b\s\w\ir\x\w\llvm_build\tools\clang\include -IC:\b\s\w\ir\x\w\recipe_cleanup\tensorflow-venv\store\python_venv-q9i5kpsp0iun0ktmqgab125ti8\contents\Lib\site-packages\tensorflow\include -IC:\b\s\w\ir\x\w\llvm_build\include -IC:\b\s\w\ir\x\w\llvm-llvm-project\llvm\include -IC:\b\s\w\ir\x\w\llvm-llvm-project\clang-tools-extra\clang-include-fixer\tool\.. -imsvcC:\b\s\w\ir\x\w\zlib_install_target\include -imsvcC:\b\s\w\ir\x\w\zstd_install\include /DWIN32 /D_WINDOWS   /Zc:inline /Zc:__cplusplus /Oi /Brepro /bigobj /permissive- /W4  -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wmisleading-indentation -Wctad-maybe-unsupported /Gw -no-canonical-prefixes /O2 /Ob2  -std:c++17 -MT  /EHs-c- /GR- -UNDEBUG /showIncludes /Fotools\clang\tools\extra\clang-include-fixer\tool\CMakeFiles\clang-include-fixer.dir\ClangIncludeFixer.cpp.obj /Fdtools\clang\tools\extra\clang-include-fixer\tool\CMakeFiles\clang-include-fixer.dir\ -c -- C:\b\s\w\ir\x\w\llvm-llvm-project\clang-tools-extra\clang-include-fixer\tool\ClangIncludeFixer.cpp
In file included from C:\b\s\w\ir\x\w\llvm-llvm-project\clang-tools-extra\clang-include-fixer\tool\ClangIncludeFixer.cpp:11:
In file included from C:\b\s\w\ir\x\w\llvm-llvm-project\clang-tools-extra\clang-include-fixer\tool\..\IncludeFixer.h:15:
In file included from C:\b\s\w\ir\x\w\llvm-llvm-project\clang\include\clang/Sema/ExternalSemaSource.h:15:
In file included from C:\b\s\w\ir\x\w\llvm-llvm-project\clang\include\clang/AST/ExternalASTSource.h:18:
In file included from C:\b\s\w\ir\x\w\llvm-llvm-project\clang\include\clang/AST/DeclBase.h:18:
In file included from C:\b\s\w\ir\x\w\llvm-llvm-project\clang\include\clang/AST/DeclarationName.h:18:
In file included from C:\b\s\w\ir\x\w\llvm-llvm-project\clang\include\clang/Basic/IdentifierTable.h:18:
In file included from C:\b\s\w\ir\x\w\llvm-llvm-project\clang\include\clang/Basic/Builtins.h:63:
C:\b\s\w\ir\x\w\llvm_build\tools\clang\include\clang/Basic/Builtins.inc(151,1): error: redefinition of enumerator 'BI_alloca'
  151 | LANGBUILTIN(_alloca, "v*z", "n", ALL_MS_LANGUAGES)
      | ^
C:\b\s\w\ir\x\w\llvm_build\tools\clang\include\clang/Basic/Builtins.inc(15,54): note: expanded from macro 'LANGBUILTIN'
   15 | #  define LANGBUILTIN(ID, TYPE, ATTRS, BUILTIN_LANG) BUILTIN(ID, TYPE, ATTRS)
      |                                                      ^
C:\b\s\w\ir\x\w\llvm-llvm-project\clang\include\clang/Basic/Builtins.h(62,34): note: expanded from macro 'BUILTIN'
   62 | #define BUILTIN(ID, TYPE, ATTRS) BI##ID,
      |                                  ^
<scratch space>(72,1): note: expanded from here
   72 | BI_alloca
      | ^
C:\b\s\w\ir\x\w\llvm_build\tools\clang\include\clang/Basic/Builtins.inc(150,1): note: previous definition is here
  150 | LIBBUILTIN(alloca, "v*z", "fn", STDLIB_H, ALL_GNU_LANGUAGES)
      | ^
C:\b\s\w\ir\x\w\llvm_build\tools\clang\include\clang/Basic/Builtins.inc(11,61): note: expanded from macro 'LIBBUILTIN'
   11 | #  define LIBBUILTIN(ID, TYPE, ATTRS, HEADER, BUILTIN_LANG) BUILTIN(ID, TYPE, ATTRS)
      |                                                             ^
C:\b\s\w\ir\x\w\llvm-llvm-project\clang\include\clang/Basic/Builtins.h(62,34): note: expanded from macro 'BUILTIN'
   62 | #define BUILTIN(ID, TYPE, ATTRS) BI##ID,
      |                                  ^
<scratch space>(71,1): note: expanded from here
   71 | BI_alloca
      | ^

[llvmbot]

@llvm/pr-subscribers-clang

Author: Prabhuk (Prabhuk)

Changes

Reverts llvm/llvm-project#81534

llvm/llvm-project#81534 breaks building (Fuchsia) Clang toolchain on Windows.

Log: https://logs.chromium.org/logs/fuchsia/buildbucket/cr-buildbucket/8756186536543250705/+/u/clang/install/stdout
Builder: https://ci.chromium.org/ui/p/fuchsia/builders/toolchain.ci/clang-windows-x64/b8756186536543250705/overview

FAILED: tools/clang/tools/extra/clang-include-fixer/tool/CMakeFiles/clang-include-fixer.dir/ClangIncludeFixer.cpp.obj 
C:\b\s\w\ir\x\w\cipd\bin\clang-cl.exe  /nologo -TP -DCLANG_REPOSITORY_STRING=\"https://llvm.googlesource.com/llvm-project\" -DGTEST_HAS_RTTI=0 -DUNICODE -D_CRT_NONSTDC_NO_DEPRECATE -D_CRT_NONSTDC_NO_WARNINGS -D_CRT_SECURE_NO_DEPRECATE -D_CRT_SECURE_NO_WARNINGS -D_GLIBCXX_ASSERTIONS -D_HAS_EXCEPTIONS=0 -D_SCL_SECURE_NO_DEPRECATE -D_SCL_SECURE_NO_WARNINGS -D_UNICODE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -IC:\b\s\w\ir\x\w\llvm_build\tools\clang\tools\extra\clang-include-fixer\tool -IC:\b\s\w\ir\x\w\llvm-llvm-project\clang-tools-extra\clang-include-fixer\tool -IC:\b\s\w\ir\x\w\llvm-llvm-project\clang\include -IC:\b\s\w\ir\x\w\llvm_build\tools\clang\include -IC:\b\s\w\ir\x\w\recipe_cleanup\tensorflow-venv\store\python_venv-q9i5kpsp0iun0ktmqgab125ti8\contents\Lib\site-packages\tensorflow\include -IC:\b\s\w\ir\x\w\llvm_build\include -IC:\b\s\w\ir\x\w\llvm-llvm-project\llvm\include -IC:\b\s\w\ir\x\w\llvm-llvm-project\clang-tools-extra\clang-include-fixer\tool\.. -imsvcC:\b\s\w\ir\x\w\zlib_install_target\include -imsvcC:\b\s\w\ir\x\w\zstd_install\include /DWIN32 /D_WINDOWS   /Zc:inline /Zc:__cplusplus /Oi /Brepro /bigobj /permissive- /W4  -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wmisleading-indentation -Wctad-maybe-unsupported /Gw -no-canonical-prefixes /O2 /Ob2  -std:c++17 -MT  /EHs-c- /GR- -UNDEBUG /showIncludes /Fotools\clang\tools\extra\clang-include-fixer\tool\CMakeFiles\clang-include-fixer.dir\ClangIncludeFixer.cpp.obj /Fdtools\clang\tools\extra\clang-include-fixer\tool\CMakeFiles\clang-include-fixer.dir\ -c -- C:\b\s\w\ir\x\w\llvm-llvm-project\clang-tools-extra\clang-include-fixer\tool\ClangIncludeFixer.cpp
In file included from C:\b\s\w\ir\x\w\llvm-llvm-project\clang-tools-extra\clang-include-fixer\tool\ClangIncludeFixer.cpp:11:
In file included from C:\b\s\w\ir\x\w\llvm-llvm-project\clang-tools-extra\clang-include-fixer\tool\..\IncludeFixer.h:15:
In file included from C:\b\s\w\ir\x\w\llvm-llvm-project\clang\include\clang/Sema/ExternalSemaSource.h:15:
In file included from C:\b\s\w\ir\x\w\llvm-llvm-project\clang\include\clang/AST/ExternalASTSource.h:18:
In file included from C:\b\s\w\ir\x\w\llvm-llvm-project\clang\include\clang/AST/DeclBase.h:18:
In file included from C:\b\s\w\ir\x\w\llvm-llvm-project\clang\include\clang/AST/DeclarationName.h:18:
In file included from C:\b\s\w\ir\x\w\llvm-llvm-project\clang\include\clang/Basic/IdentifierTable.h:18:
In file included from C:\b\s\w\ir\x\w\llvm-llvm-project\clang\include\clang/Basic/Builtins.h:63:
C:\b\s\w\ir\x\w\llvm_build\tools\clang\include\clang/Basic/Builtins.inc(151,1): error: redefinition of enumerator 'BI_alloca'
  151 | LANGBUILTIN(_alloca, "v*z", "n", ALL_MS_LANGUAGES)
      | ^
C:\b\s\w\ir\x\w\llvm_build\tools\clang\include\clang/Basic/Builtins.inc(15,54): note: expanded from macro 'LANGBUILTIN'
   15 | #  define LANGBUILTIN(ID, TYPE, ATTRS, BUILTIN_LANG) BUILTIN(ID, TYPE, ATTRS)
      |                                                      ^
C:\b\s\w\ir\x\w\llvm-llvm-project\clang\include\clang/Basic/Builtins.h(62,34): note: expanded from macro 'BUILTIN'
   62 | #define BUILTIN(ID, TYPE, ATTRS) BI##ID,
      |                                  ^
<scratch space>(72,1): note: expanded from here
   72 | BI_alloca
      | ^
C:\b\s\w\ir\x\w\llvm_build\tools\clang\include\clang/Basic/Builtins.inc(150,1): note: previous definition is here
  150 | LIBBUILTIN(alloca, "v*z", "fn", STDLIB_H, ALL_GNU_LANGUAGES)
      | ^
C:\b\s\w\ir\x\w\llvm_build\tools\clang\include\clang/Basic/Builtins.inc(11,61): note: expanded from macro 'LIBBUILTIN'
   11 | #  define LIBBUILTIN(ID, TYPE, ATTRS, HEADER, BUILTIN_LANG) BUILTIN(ID, TYPE, ATTRS)
      |                                                             ^
C:\b\s\w\ir\x\w\llvm-llvm-project\clang\include\clang/Basic/Builtins.h(62,34): note: expanded from macro 'BUILTIN'
   62 | #define BUILTIN(ID, TYPE, ATTRS) BI##ID,
      |                                  ^
<scratch space>(71,1): note: expanded from here
   71 | BI_alloca
      | ^

---

Full diff: https://github.com/llvm/llvm-project/pull/81649.diff

1 Files Affected:

• (modified) clang/include/clang/Basic/Builtins.h (+4)

diff --git a/clang/include/clang/Basic/Builtins.h b/clang/include/clang/Basic/Builtins.h
index 6700d1903a0088..f955d21169556a 100644
--- a/clang/include/clang/Basic/Builtins.h
+++ b/clang/include/clang/Basic/Builtins.h
@@ -20,6 +20,10 @@
 #include "llvm/ADT/StringRef.h"
 #include <cstring>
 
+// VC++ defines 'alloca' as an object-like macro, which interferes with our
+// builtins.
+#undef alloca
+
 namespace clang {
 class TargetInfo;
 class IdentifierTable;

[aeubanks]

for my information, which version of Visual Studio are you using?

[Prabhuk]

We don't use MSVC. CC: @zeroomega

[zeroomega]

for my information, which version of Visual Studio are you using?

To be precise, we don't use (not installed) full Visual Studio. We directly install Visual Studio build tools from VS2022.
The MSVC version string is 14.34.31933 with Windows Kit 10.0.19041.0