Hi!
On Dec 20, Davi Arnaut wrote:
> ChangeSet@stripped, 2007-12-20 15:11:16-02:00, davi@stripped +3 -0
> Bug#31891 Meaningful stack trace
>
> Currently, when the MySQL server crashes, the generated stack
> dump is numeric and needs external tools to properly resolve
> the functions names. The problem is that this is not very helpful
> to someone who has a limited knowledge of debugging techniques.
> Also the generated stack trace only contains the functions names
> and requires special code for each platform (because of different
> stack layouts).
>
> Nowadays, newer versions of the GNU C Library provides a set of
> functions to obtain and manipulate a stack traces from within the
> program. On systems that use teh ELF binary format, the stack trace
> will contain important informations such as the shared object where
> the call was generated, an offset into the function, and the actual
> return address, and on other systems, only the return address is
> presented -- which equals the current MySQL stack trace. Currently,
> the library generates meaningful stack traces on the following
> platforms: i386, x86_64, powerpc, ia64, alpha and s390. Having
> the function name also makes possible the name demangling of
> C++ functions.
I would prefer a shorter changeset comment. It doesn't need to be a
novel, a short summary is enough. For example:
Bug#31891 Meaningful stack trace
On crashes generate a user-friendly resolved and demangled stack
trace when libc provides the necessary functions (newer libc on i386,
x86_64, powerpc, ia64, alpha and s390). Otherwise print a numeric
stack trace as before, relying on resolve_stack_dump utility.
> diff -Nrup a/sql/stacktrace.c b/sql/stacktrace.c
> --- a/sql/stacktrace.c 2007-07-23 14:39:47 -03:00
> +++ b/sql/stacktrace.c 2007-12-20 15:11:14 -02:00
> @@ -93,9 +98,82 @@ inline uint32* find_prev_pc(uint32* pc,
> }
> #endif /* defined(__alpha__) && defined(__GNUC__) */
>
> +#if HAVE_BACKTRACE && HAVE_ABI_CXA_DEMANGLE && HAVE_WEAK_SYMBOL
> +#define BACKTRACE_DEMANGLE 1
> +#endif
> +
> +#ifdef BACKTRACE_DEMANGLE
> +
> +char *__cxa_demangle(const char *mangled_name, char *output_buffer,
> + unsigned int *length, int *status) __attribute__((__weak__));
> +
> +static char *my_demangle(const char *mangled_name, int *status)
> +{
> + if (__cxa_demangle)
> + return __cxa_demangle(mangled_name, NULL, NULL, status);
> + else
> + return NULL;
> +}
Aren't you overdoing it ?
Why are you doing configure check for __cxa_demangle and configure check
for __weak__ and runtime detection of __cxa_demangle ?
I'd say that only configure check for __cxa_demangle is enough.
Or - if you really believe that it's widespread to have libraries with
and without __cxa_demangle on systems where the same mysqld binary can
be run (and thus runtime detection is necessary) - why do you do
configure-time check for __cxa_demangle and weak ?
> +static void my_demangle_symbols(char **addrs, int n)
> +{
> + int status, i;
> + char *begin, *end, *demangled;
> +
> + for (i= 0; i < n; i++)
> + {
> + demangled= NULL;
> + begin= strchr(addrs[i], '(');
> + end= begin ? strchr(begin, '+') : NULL;
> +
> + if (begin && end)
> + {
> + *begin++= *end++= '\0';
> + demangled= my_demangle(begin, &status);
> + if (!demangled || status)
> + {
> + demangled= NULL;
> + begin[-1]= '(';
> + end[-1]= '+';
> + }
> + }
> +
> + if (demangled)
> + fprintf(stderr, "%s(%s+%s\n", addrs[i], demangled, end);
> + else
> + fprintf(stderr, "%s\n", addrs[i]);
> + }
> +}
> +#endif
> +
> +
> +#if HAVE_BACKTRACE
> +static void backtrace_current_thread(void)
> +{
> + void *addrs[32];
I'd have a larger array here - we have few recursive functions, and I
believe 32 may be not enough.
> + char **strings= NULL;
> + int n = backtrace(addrs, array_elements(addrs));
> +#ifdef BACKTRACE_DEMANGLE
> + if ((strings= backtrace_symbols(addrs, n)))
> + {
> + my_demangle_symbols(strings, n);
> + free(strings);
> + }
> + else
> +#endif
> + {
> + backtrace_symbols_fd(addrs, n, fileno(stderr));
> + }
> +}
> +#endif
> +
Regards / Mit vielen Grüssen,
Sergei
--
__ ___ ___ ____ __
/ |/ /_ __/ __/ __ \/ / Sergei Golubchik <serg@stripped>
/ /|_/ / // /\ \/ /_/ / /__ Principal Software Developer
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