[LLVMbugs] [Bug 11457] New: GCOV .gcda file is overwritten, not appended

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=11457

             Bug #: 11457
           Summary: GCOV .gcda file is overwritten, not appended
           Product: clang
           Version: unspecified
          Platform: Macintosh
        OS/Version: MacOS X
            Status: NEW
          Severity: normal
          Priority: P
         Component: -New Bugs
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: bjhomer+llvm at gmail.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified


According to the GCC documentation[1], execution counts stored in .gcda files
are intended to be cumulative across multiple runs. This is useful, for
example, when a user has multiple test suites that run as separate processes.
Currently, the execution counts stored for any given file are those that were
stored by the last test process that touched that file, ignoring runs by
previous processes.

For example, I have an application (with unit tests) that relies on a library
(with its own unit tests). The application's test suite invokes some of the
library's methods, but is not intended to fully test the library. I have an
Xcode scheme set up to run both the library unit tests and the application unit
tests. Currently, if I run only the library unit tests, given files have 100%
test coverage. However, if I run both the library and application test suites,
those same files show >100% coverage, because it's only showing what the
application tests exercised, and discarding what the library tests exercised.

[1]: http://gcc.gnu.org/onlinedocs/gcc/Invoking-Gcov.html

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