[llvm-bugs] [Bug 24847] New: IR linking and COMDAT constraints

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=24847

            Bug ID: 24847
           Summary: IR linking and COMDAT constraints
           Product: libraries
           Version: 3.7
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: normal
          Priority: P
         Component: Linker
          Assignee: unassignedbugs at nondot.org
          Reporter: russell.wallace at gmail.com
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

Created attachment 14888
  --> https://llvm.org/bugs/attachment.cgi?id=14888&action=edit
The linked .ll file

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
#include <regex>

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)

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