LLVM linking problem

When I use clang on Windows to compile a program using regular expressions to intermediate code, then run the result through llvm-link and finally try to generate an executable, I get an error.

All of these ingredients are necessary; it works if the program doesn’t use regular expressions, and it works if I compile it directly instead of going via intermediate code.

The use of the exact llvm-link binary, however, is not a necessary ingredient; I get the same result with a linking program of my own that uses the same libraries as llvm-link.

Minimal test case:

C:\test>type test.cpp

int main() {
std::cmatch m;
regex_match(“a”, m, std::regex(“a”));
return 0;

C:\test>clang-cl -Xclang -emit-llvm -c -fms-compatibility-version=19 test.cpp

C:\test>move test.obj test.ll
Overwrite C:\test\test.ll? (Yes/No/All): y
1 file(s) moved.

C:\test>llvm-link test.ll -o=a.ll

C:\test>clang-cl -Wno-override-module a.ll
a-e22d14.obj : fatal error LNK1243: invalid or corrupt file: COMDAT section 0x373 associated with following section 0x389
clang-cl.exe: error: linker command failed with exit code 1243 (use -v to see invocation)

C:\test>llvm-link -version
LLVM (http://llvm.org/):
LLVM version 3.7.0
DEBUG build.
Default target: x86_64-pc-windows-msvc
Host CPU: sandybridge

That’s pretty neat. Can you file a bug and attach a compressed version of a.ll? It looks like link.exe has interesting ordering constraints around associative COMDATs that we haven’t run into before.