Undefined reference to global variable defined in the same file (in MSVC mode)

[adalisk-emikhaylov]

struct A
{
    ~A() {}
};

struct B
{
    int b = 0;
    B(A) {}
};

struct C : public B
{
    using B::B;
};

C var = A{};

int main()
{
    return var.b;
}

Building this on Windows produces following error:

lld-link: error: undefined symbol: struct C var
>>> referenced by C:\msys2\tmp\1-93d998.o:(main)
clang++: error: linker command failed with exit code 1 (use -v to see invocation)

The compiler invocation is clang++ 1.cpp -fuse-ld=lld (similar error without LLD, using it to show a non-localized message).

Clang version is:

$ clang++ --version
clang version 16.0.0
Target: x86_64-pc-windows-msvc
Thread model: posix

This doesn't happen on Linux or in MinGW-compatibility mode.

Making the variable static doesn't change the result. Making it inline ICEs the compiler:

fatal error: error in backend: Associative COMDAT symbol '?var@@3UC@@A' is not a key for its COMDAT.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace, preprocessed source, and associated run script.
Stack dump:
0.      Program arguments: D:\\Tools\\LLVM_16\\bin\\clang++.exe -cc1 -triple x86_64-pc-windows-msvc19.29.30136 -emit-obj -mrelax-all -mincremental-linker-compatible -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name 1.cpp -mrelocation-model pic -pic-level 2 -mframe-pointer=none -fmath-errno -ffp-contract=on -fno-rounding-math -mconstructor-aliases -funwind-tables=2 -target-cpu x86-64 -tune-cpu generic -mllvm -treat-scalable-fixed-error-as-warning -fcoverage-compilation-dir=D:\\Repos\\sandbox -resource-dir D:\\Tools\\LLVM_16\\lib\\clang\\16 -internal-isystem D:\\Tools\\LLVM_16\\lib\\clang\\16\\include -internal-isystem "C:\\Program Files (x86)\\Microsoft Visual Studio\\2019\\Community\\VC\\Tools\\MSVC\\14.29.30133\\include" -internal-isystem "C:\\Program Files (x86)\\Microsoft Visual Studio\\2019\\Community\\VC\\Tools\\MSVC\\14.29.30133\\atlmfc\\include" -internal-isystem "C:\\Program Files (x86)\\Windows Kits\\10\\Include\\10.0.18362.0\\ucrt" -internal-isystem "C:\\Program Files (x86)\\Windows Kits\\10\\Include\\10.0.18362.0\\shared" -internal-isystem "C:\\Program Files (x86)\\Windows Kits\\10\\Include\\10.0.18362.0\\um" -internal-isystem "C:\\Program Files (x86)\\Windows Kits\\10\\Include\\10.0.18362.0\\winrt" -internal-isystem "C:\\Program Files (x86)\\Windows Kits\\10\\Include\\10.0.18362.0\\cppwinrt" -fdeprecated-macro -fdebug-compilation-dir=D:\\Repos\\sandbox -ferror-limit 19 -fmessage-length=251 -fno-use-cxa-atexit -fms-extensions -fms-compatibility -fms-compatibility-version=19.29.30136 -std=c++14 -fdelayed-template-parsing -fcxx-exceptions -fexceptions -fcolor-diagnostics -faddrsig -o C:\\msys2\\tmp\\1-cc1f29.o -x c++ 1.cpp
1.      <eof> parser at end of file
2.      Code generation
clang++: error: clang frontend command failed with exit code 70 (use -v to see invocation)

# Crash reproducer for clang version 16.0.0
# Driver args: "--driver-mode=g++" "1.cpp" "-fuse-ld=lld"
# Original command:  "D:\\Tools\\LLVM_16\\bin\\clang++.exe" "-cc1" "-triple" "x86_64-pc-windows-msvc19.29.30136" "-emit-obj" "-mrelax-all" "-mincremental-linker-compatible" "-disable-free" "-clear-ast-before-backend" "-disable-llvm-verifier" "-discard-value-names" "-main-file-name" "1.cpp" "-mrelocation-model" "pic" "-pic-level" "2" "-mframe-pointer=none" "-fmath-errno" "-ffp-contract=on" "-fno-rounding-math" "-mconstructor-aliases" "-funwind-tables=2" "-target-cpu" "x86-64" "-tune-cpu" "generic" "-mllvm" "-treat-scalable-fixed-error-as-warning" "-fcoverage-compilation-dir=D:\\Repos\\sandbox" "-resource-dir" "D:\\Tools\\LLVM_16\\lib\\clang\\16" "-internal-isystem" "D:\\Tools\\LLVM_16\\lib\\clang\\16\\include" "-internal-isystem" "C:\\Program Files (x86)\\Microsoft Visual Studio\\2019\\Community\\VC\\Tools\\MSVC\\14.29.30133\\include" "-internal-isystem" "C:\\Program Files (x86)\\Microsoft Visual Studio\\2019\\Community\\VC\\Tools\\MSVC\\14.29.30133\\atlmfc\\include" "-internal-isystem" "C:\\Program Files (x86)\\Windows Kits\\10\\Include\\10.0.18362.0\\ucrt" "-internal-isystem" "C:\\Program Files (x86)\\Windows Kits\\10\\Include\\10.0.18362.0\\shared" "-internal-isystem" "C:\\Program Files (x86)\\Windows Kits\\10\\Include\\10.0.18362.0\\um" "-internal-isystem" "C:\\Program Files (x86)\\Windows Kits\\10\\Include\\10.0.18362.0\\winrt" "-internal-isystem" "C:\\Program Files (x86)\\Windows Kits\\10\\Include\\10.0.18362.0\\cppwinrt" "-fdeprecated-macro" "-fdebug-compilation-dir=D:\\Repos\\sandbox" "-ferror-limit" "19" "-fmessage-length=251" "-fno-use-cxa-atexit" "-fms-extensions" "-fms-compatibility" "-fms-compatibility-version=19.29.30136" "-std=c++14" "-fdelayed-template-parsing" "-fcxx-exceptions" "-fexceptions" "-fcolor-diagnostics" "-faddrsig" "-o" "C:\\msys2\\tmp\\1-cc1f29.o" "-x" "c++" "1.cpp"
 "D:\\Tools\\LLVM_16\\bin\\clang++.exe" "-cc1" "-triple" "x86_64-pc-windows-msvc19.29.30136" "-emit-obj" "-mrelax-all" "-mincremental-linker-compatible" "-disable-free" "-clear-ast-before-backend" "-disable-llvm-verifier" "-discard-value-names" "-main-file-name" "1.cpp" "-mrelocation-model" "pic" "-pic-level" "2" "-mframe-pointer=none" "-fmath-errno" "-ffp-contract=on" "-fno-rounding-math" "-mconstructor-aliases" "-funwind-tables=2" "-target-cpu" "x86-64" "-tune-cpu" "generic" "-mllvm" "-treat-scalable-fixed-error-as-warning" "-fcoverage-compilation-dir=D:\\Repos\\sandbox" "-fdeprecated-macro" "-fdebug-compilation-dir=D:\\Repos\\sandbox" "-ferror-limit" "19" "-fmessage-length=251" "-fno-use-cxa-atexit" "-fms-extensions" "-fms-compatibility" "-fms-compatibility-version=19.29.30136" "-std=c++14" "-fdelayed-template-parsing" "-fcxx-exceptions" "-fexceptions" "-fcolor-diagnostics" "-faddrsig" "-x" "c++" "1-df2247.cpp"

[llvmbot]

@llvm/issue-subscribers-clang-codegen

[efriedma-quic]

The following reproduces on all targets:

struct B
{
    B(int,...) {}
};

struct C : public B
{
    using B::B;
};

C var = 3;

It looks like EmitInlinedInheritingCXXConstructorCall is accidentally changing the name of the global variable to "this".

[efriedma-quic]

llvm-project/clang/lib/CodeGen/CGDecl.cpp

Line 2456 in bb3763e

Arg.getAnyValue()->setName(D.getName());

[efriedma-quic]

https://reviews.llvm.org/D154270