Re: Printing backtrace of postgres processes

On 2024-Feb-09, Michael Paquier wrote:

> Anyway, I've been digging around the signal-safety of backtrace(3)
> (even looking a bit at some GCC code, brrr), and I am under the
> impression that backtrace() is just by nature not safe and also
> dangerous in signal handlers.  One example of issue I've found:
> https://github.com/gperftools/gperftools/issues/838
> 
> This looks like enough ground to me to reject the patch.

Hmm, but the backtrace() manpage says

       •  backtrace() and backtrace_symbols_fd() don't call malloc()  explic‐
          itly,  but  they  are part of libgcc, which gets loaded dynamically
          when first used.  Dynamic loading usually triggers a call  to  mal‐
          loc(3).   If  you  need certain calls to these two functions to not
          allocate memory (in signal handlers, for example), you need to make
          sure libgcc is loaded beforehand.

and the patch ensures that libgcc is loaded by calling a dummy
backtrace() at the start of the process.

-- 
Álvaro Herrera               48°01'N 7°57'E  —  https://www.EnterpriseDB.com/
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