On 2020-07-17, Julian Smith wrote:
> For me, backtrace_symbols() does not show line-numbers. Is this the
> intended behaviour?
It is working as shown in upstream's example:
https://github.com/conformal/backtrace/wiki
So I'd say this is as expected.
> I'm using:
> OpenBSD jules-obsd 6.7 GENERIC.MP#182 amd64
> libexecinfo-0.3p2v0
>
> With 'cc -g -Wl,--export-dynamic', i'm getting backtraces like:
>
> 0x69854ee369 at ./foo.c.exe
> 0x69854ee477 at ./foo.c.exe
> 0x69854ee4be at ./foo.c.exe
> 0x69854ee13b <__start+315> at ./foo.c.exe
>
> [gdb can show line numbers on the same executable, so the information
> is definitely in the executable somewhere.]
>
> I'm testing with this code:
>
>
> #include
> #include
> #include
> #include
>
> void bar()
> {
> void* bt[20];
> char** strings;
> int i;
> int d;
>
> d = backtrace(bt, sizeof(bt) / sizeof(bt[0]));
> if (d == -1)
> errx(1, "backtrace");
>
> strings = backtrace_symbols(bt, d);
>
> if (strings == NULL)
> errx(1, "backtrace_symbols");
>
> for (i = 0; i < d; i++)
> printf("%s\n", strings[i]);
>
> free(strings);
> }
>
> void foo(void)
> {
> bar();
> }
>
> int main(void)
> {
> foo();
> return 0;
> }
>===
>
> Build with:
> cc -g -o foo.c.exe foo.c -I /usr/local/include -g -L /usr/local/lib
> -lexecinfo -Wl,--export-dynamic
>
> Run:
> ./foo.c.exe
>
> Output:
> 0x69854ee369 at ./foo.c.exe
> 0x69854ee477 at ./foo.c.exe
> 0x69854ee4be at ./foo.c.exe
> 0x69854ee13b <__start+315> at ./foo.c.exe
>
>
>
>
> Also, here's a small diff for /usr/local/man/man3/backtrace.3, which
> makes the code example more directly usable and fixes a misprint of
> '\n':
>
> --- /usr/local/man/man3/backtrace.3 Fri May 8 19:49:25 2020
> +++ backtrace.3 Fri Jul 17 11:09:15 2020
> @@ -63,14 +63,17 @@
> The following code fragment illustrates the use of the backtrace
> functionality:
> .Bd -literal -offset indent
> +#include
> +#include
> +
> void
> print_backtrace(void)
> {
> - void*bt[BT_MAX_DEPTH];
> + void*bt[20];
> char**strings;
> int i, d;
>
> -d = backtrace(bt, BT_MAX_DEPTH);
> +d = backtrace(bt, sizeof(bt) / sizeof(bt[0]));
> if (d == -1)
> errx(1, "backtrace");
>
> @@ -80,7 +83,7 @@
> errx(1, "backtrace_symbols");
>
> for (i = 0; i < d; i++)
> - printf("%s\n", strings[i]);
> + printf("%s\\n", strings[i]);
>
> free(strings);
> }
>
> Thanks,
>
> - Jules
>
