On Mon, Sep 3, 2012 at 7:55 AM, Malte Forkel <malte.forkel@xxxxxxxxx> wrote: > > I need some help with tracing function calls using function > instrumentation (__cyg_profile_func_enter and __cyg_profile_func_exit) > as suggsted in the GDB FAQ (http://sourceware.org/gdb/wiki/FAQ#line-62). > > Jan Kratochvil's itrace mentioned in the FAQ can be used to print the > names of both the called function and the calling function. It uses the > elfutls/dwfl library to retrieve the DWARF information. I tried to > extend itrace to also give the name of the source file and the line > numbers for each function call. > > But I found that the line numbers always seems to refer to the "next" > unit in the source code, e.g. to the compound statement instead of to > the declarator for this_fn (the caller) and to the statement after the > actual function call for the call_site (callee). > > This effect might be caused to the way instrumentation works. I don't > suspect the DWARF information and the dwfl library to be wrong. But of > course there could easily be a flaw in my use of the dwfl library. Here > is - without most declarations and all error checking (some return > values can be NULL) - how I try to retrieve the source information for > 'this_fn' and 'call_site': > > static const char *addr_print (void *addr) > { > Dwarf_AAdrr address = (ptrdiff_t) addr; > Dwfl *dwfl = dwfl_get (); > ... > mod = dwfl_addrmodule (dwfl, address); > name = dwfl_module_addrname (mod, address); > line = dwfl_module_getsrc (mod, address); > fname = dwfl_lineinfo (line, NULL, &lineno, &colno, NULL, NULL); > ... > } > > If the is a value written to 'lineno at' all, it is "off by one". > > Finding the "real" line number for a function definiton given the line > number of its statement block should be easy. Finding the "real" line > number of the statement with the function call given the line number of > the next statement might be much harder. > > So, two questions: Are the source references really "off by one" or is > it all my fault? And if it is not my fault: How do I get the correct > line numbers (in order to link into the Doxygen documentation). I don't know anything about dwfl. But you haven't showed us the important piece of information: where does addr come from in the call to addr_print? Ian
