Re: Changes in inline behavior on O2 optimization level for GCC 10+

On Sun, Jul 27, 2025 at 5:48 PM Alexey Makhmutov
<a(dot)makhmutov(at)postgrespro(dot)ru> wrote:
> The primary goal of this message is just to raise an awareness of this
> change and its possible influence on resulting builds.

I believe that clang works in the same way, and has for some time now.
"clang -mllvm -debug" output shows debug instrumentation that can
demonstrate that clang may inline functions that are not declared
"static inline" (and decline to inline functions that are). As I
understand it, to clang, the "inline" directive just lowers the
threshold at which a function will be inlined.

> Theoretically speaking, this change is not an issue by itself, as each
> compiler is in its right to adjust its optimization logic. Certain build
> pipeline could always have adjusted parameters if its maintainer is
> unsatisfied with default compiler heuristics.

"pg_attribute_always_inline" can be used to force the compiler to
inline a function. I'd be very surprised if GCC 10 failed to honor the
underlying "__attribute__((always_inline))" function attribute.

--
Peter Geoghegan