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MESAHub / mesa

Modules for Experiments in Stellar Astrophysics
http://mesastar.org
GNU Lesser General Public License v2.1
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utils: mark mesa_error with NORETURN (gcc only) #708

Open VincentVanlaer opened 3 months ago

VincentVanlaer commented 3 months ago

This means that the function will never return to its caller. This makes life easier for the optimizer and can prevent spurious maybe-uninitialized warnings.

This change was triggered by warnings in the mtx module about potentially uninitialized variables after allocation. mesa_error was used to terminate MESA if allocate would fail. Inspection of the intermediate representation of GCC showed that it considered execution to continue after mesa_error, which muddied the control flow blocks. To actually trigger a spurious warning, the variable needs to have rank > 1, be declared with pointer, and have unknown size at compile time. This is quite niche, but future changes to warnings & optimizations might change this. At least adding this attribute may make the generated assembly smaller (this was the case for a simple test function).

ifort does not seem to have a similar attribute.

VincentVanlaer commented 3 months ago

Since this seems to fail on older SDK versions and I can't find an easy way to let GCC ignore unknown attributes, feel free to close. I expect the impact of this change to be quite small in any case.