Data File Relocation to Support Cross-Profiling¶
Running the program will cause profile output to be generated. For each
source file compiled with -fprofile-arcs, an accompanying .gcda
file will be placed in the object file directory. That implicitly requires
running the program on the same system as it was built or having the same
absolute directory structure on the target system. The program will try
to create the needed directory structure, if it is not already present.
To support cross-profiling, a program compiled with -fprofile-arcs
can relocate the data files based on two environment variables:
GCOV_PREFIX contains the prefix to add to the absolute paths in the object file. Prefix can be absolute, or relative. The default is no prefix.
GCOV_PREFIX_STRIP indicates the how many initial directory names to strip off the hardwired absolute paths. Default value is 0.
Note
If GCOV_PREFIX_STRIP is set without GCOV_PREFIX is undefined, then a relative path is made out of the hardwired absolute paths.
For example, if the object file /user/build/foo.o was built with
-fprofile-arcs, the final executable will try to create the data file
/user/build/foo.gcda when running on the target system. This will
fail if the corresponding directory does not exist and it is unable to create
it. This can be overcome by, for example, setting the environment as
GCOV_PREFIX=/target/run and GCOV_PREFIX_STRIP=1. Such a
setting will name the data file /target/run/build/foo.gcda.
You must move the data files to the expected directory tree in order to
use them for profile directed optimizations ( -fprofile-use ), or to
use the gcov tool.