Hello Stefan
Long after the fact... sorry!
On 12/05/2014 06:04 PM, Stefan Puiu wrote:
Hi Walter,
On Fri, Dec 5, 2014 at 5:18 PM, walter harms <wharms@xxxxxx> wrote:
+So you need to call
+.BR backtrace ()
+or some other libgcc function early in your program to trigger loading
+of libgcc in order to make sure that later calls don't trigger the
+indirect memory allocation (for instance when called from a signal
+handler).
I would drop that part. there are several way to load libgcc (e.g.LD_PRELOAD).
what about "make sure that libgcc is already loaded at the begining" ?
something like that.
Yep, makes sense, thanks. New version below:
Thanks; patch applied, with Reviewed-by: tag added for Walter's input.
Cheers,
Michael
diff --git a/man3/backtrace.3 b/man3/backtrace.3
index 1b21794..0b2c6ba 100644
--- a/man3/backtrace.3
+++ b/man3/backtrace.3
@@ -114,7 +114,8 @@ it writes the strings, one per line, to the file descriptor
.BR backtrace_symbols_fd ()
does not call
.BR malloc (3),
-and so can be employed in situations where the latter function might fail.
+and so can be employed in situations where the latter function might
+fail, but see NOTES.
.SH RETURN VALUE
.BR backtrace ()
returns the number of addresses returned in
@@ -156,6 +157,18 @@ violated.
Inlined functions do not have stack frames.
.IP *
Tail-call optimization causes one stack frame to replace another.
+.IP *
+.BR backtrace ()
+and
+.BR backtrace_symbols_fd ()
+don't call
+.BR malloc ()
+explicitly, but they are part of libgcc, which gets loaded dynamically
+when first used. Dynamic loading usually triggers a call to
+.BR malloc ().
+If you need certain calls to the 2 functions to not allocate memory
+(in signal handlers, for example), you need to make sure libgcc is
+loaded beforehand.
.PP
The symbol names may be unavailable without the use of special linker
options.
--
To unsubscribe from this list: send the line "unsubscribe linux-man" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
--
To unsubscribe from this list: send the line "unsubscribe linux-man" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
