Code compiled with a profiling flag does not generate gmon.out

Question

I compiled the code with gcc using the profiling flag ( -pg ), but when I run the program gmon.out is not created.
I compiled the test code - actually the one that was from this question - to see if the compilation flag and gprof work, and yes, it worked.

To compile the code (named xrttimetag ), the following line was used (below I used -I(...) and -L(...) to hide a huge list of paths to other scientific libraries):

 gcc -c -o ./xrttimetag.o -Wall --pedantic -Wno-comment -Wno-long-long -pg -fPIC -I(...) -DPACKAGE_NAME="" -DPACKAGE_TARNAME="" -DPACKAGE_VERSION="" -DPACKAGE_STRING="" -DPACKAGE_BUGREPORT="" -DPACKAGE_URL="" -Dg77Fortran=1 -DgFortran=1 -DHAVE_CONNECT=1 -DHAVE_ACCEPT=1 -DSTDC_HEADERS=1 -DHAVE_SYS_TYPES_H=1 -DHAVE_SYS_STAT_H=1 -DHAVE_STDLIB_H=1 -DHAVE_STRING_H=1 -DHAVE_MEMORY_H=1 -DHAVE_STRINGS_H=1 -DHAVE_INTTYPES_H=1 -DHAVE_STDINT_H=1 -DHAVE_UNISTD_H=1 -DHAVE_LIBM=1 -DHAVE_LIBDL=1 -DHAVE_LIBNCURSES=1 -DSIZEOF_LONG=8 xrttimetag.c gcc -o xrttimetag xrttimetag.o -L(...) -lswxrt -latFunctions3.3 -lcoordfits -lcoord -lephemeris -lhdinit_2.7 -lhdutils_2.7 -lape_2.8 -lcfitsio_3.37 -lreadline -lhdio_2.7 -lncurses -ldl -lm -L/usr/lib64/gcc/x86_64-suse-linux/4.6 -L/usr/lib64/gcc/x86_64-suse-linux/4.6/../../../../lib64 -L/lib/../lib64 -L/usr/lib/../lib64 -L/usr/lib64/gcc/x86_64-suse-linux/4.6/../../../../x86_64-suse-linux/lib -L/usr/lib64/gcc/x86_64-suse-linux/4.6/../../.. -L/usr/lib64/gcc/x86_64-suse-linux/4.6 -L/usr/lib64/gcc/x86_64-suse-linux/4.6/../../../../lib64 -L/lib/../lib64 -L/usr/lib/../lib64 -L/usr/lib64/gcc/x86_64-suse-linux/4.6/../../../../x86_64-suse-linux/lib -L/usr/lib64/gcc/x86_64-suse-linux/4.6/../../.. -lgfortran -lm -lgcc_s -lgcc -lquadmath -lm -lgcc_s -lgcc -lc -lgcc_s -lgcc "-DPACKAGE_URL =" "-Dg77Fortran = gcc -c -o ./xrttimetag.o -Wall --pedantic -Wno-comment -Wno-long-long -pg -fPIC -I(...) -DPACKAGE_NAME="" -DPACKAGE_TARNAME="" -DPACKAGE_VERSION="" -DPACKAGE_STRING="" -DPACKAGE_BUGREPORT="" -DPACKAGE_URL="" -Dg77Fortran=1 -DgFortran=1 -DHAVE_CONNECT=1 -DHAVE_ACCEPT=1 -DSTDC_HEADERS=1 -DHAVE_SYS_TYPES_H=1 -DHAVE_SYS_STAT_H=1 -DHAVE_STDLIB_H=1 -DHAVE_STRING_H=1 -DHAVE_MEMORY_H=1 -DHAVE_STRINGS_H=1 -DHAVE_INTTYPES_H=1 -DHAVE_STDINT_H=1 -DHAVE_UNISTD_H=1 -DHAVE_LIBM=1 -DHAVE_LIBDL=1 -DHAVE_LIBNCURSES=1 -DSIZEOF_LONG=8 xrttimetag.c gcc -o xrttimetag xrttimetag.o -L(...) -lswxrt -latFunctions3.3 -lcoordfits -lcoord -lephemeris -lhdinit_2.7 -lhdutils_2.7 -lape_2.8 -lcfitsio_3.37 -lreadline -lhdio_2.7 -lncurses -ldl -lm -L/usr/lib64/gcc/x86_64-suse-linux/4.6 -L/usr/lib64/gcc/x86_64-suse-linux/4.6/../../../../lib64 -L/lib/../lib64 -L/usr/lib/../lib64 -L/usr/lib64/gcc/x86_64-suse-linux/4.6/../../../../x86_64-suse-linux/lib -L/usr/lib64/gcc/x86_64-suse-linux/4.6/../../.. -L/usr/lib64/gcc/x86_64-suse-linux/4.6 -L/usr/lib64/gcc/x86_64-suse-linux/4.6/../../../../lib64 -L/lib/../lib64 -L/usr/lib/../lib64 -L/usr/lib64/gcc/x86_64-suse-linux/4.6/../../../../x86_64-suse-linux/lib -L/usr/lib64/gcc/x86_64-suse-linux/4.6/../../.. -lgfortran -lm -lgcc_s -lgcc -lquadmath -lm -lgcc_s -lgcc -lc -lgcc_s -lgcc 

I searched for characters related to gmon in the generated binary and they look a bit strange to me as they are undefined:

 readelf -s `which xrttimetag` | egrep "gmon|mcount" 21: 0000000000000000 0 NOTYPE WEAK DEFAULT UND __gmon_start__ 74: 0000000000000000 0 FUNC GLOBAL DEFAULT UND mcount@GLIBC _2.2.5 (2) 41: 000000000040267c 0 FUNC LOCAL DEFAULT 15 call_gmon_start 96: 0000000000000000 0 NOTYPE WEAK DEFAULT UND __gmon_start__ 166: 0000000000000000 0 FUNC GLOBAL DEFAULT UND mcount@ @GLIBC_2.2.5 

On the other hand, test code that I compiled with

g ++ -pg test.cpp

And searching for the characters "gmon | mcount" gives me:

 readelf -s test | egrep "gmon|mcount" 6: 0000000000000000 0 FUNC GLOBAL DEFAULT UND mcount@GLIBC _2.2.5 (3) 11: 0000000000400850 63 FUNC GLOBAL DEFAULT 15 __gmon_start__ 40: 0000000000000000 0 FILE LOCAL DEFAULT ABS gmon-start.c 43: 0000000000400890 0 FUNC LOCAL DEFAULT 15 call_gmon_start 73: 0000000000400850 63 FUNC GLOBAL DEFAULT 15 __gmon_start__ 91: 0000000000000000 0 FUNC GLOBAL DEFAULT UND mcount@ @GLIBC_2.2.5 

We can have the characters "gmon" be clearly defined for the code _ test_, and not for _xrttimetag_, but I really do not understand why. What am I missing?

Thanks.

PS: I saw the question gmon.out is not written after compiling with gcc -pg -g , and this is not duplication, unless I had completely misunderstood this.

Answer 1

You do not pass -pg when creating an executable file.

i.e.

 gcc -o xrttimetag xrttimetag.o .... 

Here you must also pass -pg . I can re-create the problem (i.e. undefined characters for gmon * calls) if I use -pg when compiling, but not when linking.

From the gcc documentation :

-pg

Create additional code to record profile information suitable for the gprof analytic program. You should use this option when compiling the source files about which you want to get data, and you should also use them when stitching.