[llvm-bugs] [Bug 43425] New: -fprofile-generate profile merging from concurrent processes fails on Windows with "LLVM Profile Error: Failed to write file ... File exists"

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=43425

            Bug ID: 43425
           Summary: -fprofile-generate profile merging from concurrent
                    processes fails on Windows with "LLVM Profile Error:
                    Failed to write file ... File exists"
           Product: new-bugs
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: hans at chromium.org
                CC: htmldeveloper at gmail.com, llvm-bugs at lists.llvm.org

For example, consider a simple program:

int main() {
        unsigned x = 1;
        for (int i = 0; i < 100*1000*1000; i++) {
                x *= i;
        }
        return 0;
}


built with instrumentation:

clang-cl -fprofile-generate=\src\tmp\ \src\tmp\a.cc

and run in an bunch of concurrent invocations (using e.g. Cygwin):

$ for i in `seq 1 100` ; do ./a.exe & done



A bunch of the program invocations fail to write their profile:

LLVM Profile Error: Failed to write file
"\src\tmp\default_15822669652030248442_0.profraw": File exists
LLVM Profile Error: Failed to write file
"\src\tmp\default_15822669652030248442_0.profraw": File exists
LLVM Profile Error: Failed to write file
"\src\tmp\default_15822669652030248442_0.profraw": File exists



(This shows up when running instrumented tablegen binaries as part of building
IR-instrumented Clang on Windows, see e.g.
https://logs.chromium.org/logs/chromium/buildbucket/cr-buildbucket.appspot.com/8901886476057032176/+/steps/package_clang/0/stdout)

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