Bugzilla Bug 204810

GCC support profile based optimization using the -fprofile-generate and
-fprofile-use options. The first instructs gcc to include hooks for the profile
data file generation, the latter uses them in the optimization step. The
profile data file is stored in the same directory as the source file, with the
suffix .gcda.
When using ccache, the input file names of gcc are replaced by temporary
(preprocessed) file names. As the file names differ between the first and the
second compilation step, gcc is unable to identify the profile data file and
can't use it.
The patch solves this problem by searching for the flags '-fprofile-generate',
'-fprofile-use' and '-fprofile-arcs'. If found, the caching is disabled and the
original gcc call (with the original input files) is performed.

Clemens

Reproducible: Always

Steps to Reproduce:
1. echo "int main(int a, char** b){}" > test.c
2. gcc -fprofile-generate -c test.c
3. gcc -fprofile-generate -o test test.o
4. ./test
5. gcc -fprofile-use -c test.c
6. gcc -o test test.o

Actual Results:  
With unpatched ccache:
5) Gives warning about $CCACHE_DIR/tmp.hash.*.gcda file not found, execution
counts assumed to be zero


Expected Results:  
With ccache:
2) Generated test.gcno in current directory
4) Generated test.gcda in current directory
5) No error.

Created an attachment (id=140402) [details]
Patch to prevent ccache from caching when -fprofile-* options are used.

Patch used in attached ebuild to fix the bug.

Created an attachment (id=140403) [details]
Modified ebuild to apply the patch

incvs.