Hi Carmelo,
>
>> Unfortunately, backtrace_symbols() is not yet ok. According to the
>> expected output of the example I took from [1], static functions
>> simply have no symbolic resolution in the glibc version; only a
>> pointer is shown.
>>
>> However, with the current uClibc / libgcc implementation, a symbolic
>> name *is* shown for static functions, but it is wrong. Referring to
>> the example code, the entry referring to myfunc2 is printed as
>> 'myfunc'. If you change the code and make myfunc static and myfunc2
>> global, then all entries referring to myfunc are printed as 'myfunc2'.
>> This is problematic in my opinion.
>>
>> I haven't looked into detail into backtrace_symbols yet. I also don't
>> know whether the error is in libgcc or libubacktrace. Any thoughts are
>> appreciated.
>>
>
> I'll give a look asap.
According to the man page of dladdr, which is used to obtain the symbol names,
"The function dladdr() takes a function pointer and tries to resolve
name and file where it is located. Information is stored in the
Dl_info structure:
typedef struct {
const char *dli_fname;/* Filename of defining object */
void *dli_fbase; /* Load address of that object */
const char *dli_sname;/* Name of nearest lower symbol */
void *dli_saddr; /* Exact value of nearest symbol */
} Dl_info;
dladdr() returns 0 on error, and non-zero on success. "
I think the 'nearest symbol' is biting us. The dladdr function doesn't
know about static functions, and hence the provided name is incorrect.
If there is a way to obtain the size of the returned symbol in some
way, then we would be able to determine whether the name is valid (by
comparing the offset). If it isn't, we just return an empty name.
Alternatively, if there would be another method that does know about
static functions, then that would help as well.
>
> Really many thanks for your feedback and testing.
You're very welcome. Thanks to you for taking this up. A backtrace
functionality is really something useful!
Best regards,
Thomas
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