[Bug rtl-optimization/20815] New: -fprofile-use barfs with "coverage mismatch for function '...' while reading counter 'arcs'."

["dank at kegel dot com" <gcc-bugzilla at gcc dot gnu dot org>]

This problem is present in at least gcc-3.4.[123], gcc-3.4-20050401, and
gcc-4.0-20050305.  I have not tested a later gcc-4.0 yet.

Create a test file pgo.cc:
 #include <iostream>
 namespace {
   void
   func() {
     std::cout << "In func" << std::endl;
   }
 }
 int main() { func(); } 

Compile it, run it, and recompile it as follows:
  i686-unknown-linux-gnu-g++  -fprofile-generate -o pgo pgo.cc 
  ./pgo
  i686-unknown-linux-gnu-g++  -fprofile-use -o pgo pgo.cc 

The -fprofile-use compilation fails with
pgo.cc: In function 'void<unnamed>::func()':
pgo.cc:6: error: coverage mismatch for function
'_ZN35_GLOBAL__N_pgo.cc_00000000_8B40D3D54funcEv' while reading counter 'arcs'.
pgo.cc:6: error: checksum is 5c057dbb instead of 3746c244

Commenting out the namespace makes the problem go away.
This keeps me from building some real apps with profile-driven optimization,
which may result in switching from gcc to icc for this app.

Thanks to Simon Baldwin for finding such a nice little test case for this.

-- 
           Summary: -fprofile-use barfs with "coverage mismatch for function
                    '...' while reading counter 'arcs'."
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: rtl-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: dank at kegel dot com
                CC: gcc-bugs at gcc dot gnu dot org
GCC target triplet: i686-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20815