instrumentation - How to instrument gcc? -

i have instrument gcc purposes. goal able track gcc functions called during particularly compile. unfortunately i'm not familiar architecture of gcc need little help. tried following steps:

1) hacking gcc/makefile.in , adding "-finstrument-functions" flag t_cflags.
2) have implemented , tested version of start_test , end_test functions. called gcc/main.c, before , after toplev_main() call. containing file linked gcc (the object added objs-common , dependency defined later in gcc/makefile.in)
3) downloading prerequisites contrib/download_prerequisites.
4) executing configuration clean build directory (on same level source dir): ./../gcc-4.6.2/configure --prefix="/opt/gcc-4.6.2/" --enable-languages="c,c++"
5) starting build "make all"

this way runned out of memory, although had 28g.
next tried remove t_cflags settings makefile , give -finstrument-functions make command: make cflags="-finstrument-functions". build successful way when tried compile resulted empty output files. (theoretically end_test should have written result given file.)

what make wrong? in advance!

unless exclude being instrumented, main subject instrumentation, placing calls start_test , end_test inside main not how want it. 'correct' way ensure file opened , closed @ right times define 'constructor' , 'destructor', , gcc automatically generates calls them before , after main:

void start_test (void)   __attribute__ ( (no_instrument_function, constructor));  void end_test (void)   __attribute__ ( (no_instrument_function, destructor));  /* file write profiling information.  */ static file *profiler_out;  void start_test (void) {   profiler_out = fopen ("profiler.out", "w");   if (profiler_out == null)     exit (-1); }  void end_test (void) {   fclose (profiler_out); } 

footnotes:

1. read more constructor, destructor , no_instrument_function attributes here. function attributes gcc understands.
2. read excellent guide instrumentation, on ibm website.