Mark functions as NORETURN #10260
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Mark functions as NORETURN #10260
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Surprisingly this leads to some code size savings on itsybitsym4, even though LTO optimization should have let the compiler deduce (almost) all of this. When a compiler knows a call can never return, it is possibly able to avoid emitting code, such as saving caller-saved registers to the stack, or doing _ANYTHING_ affter the function returns, explaining why code size savings is possible with this attribute. With the exception of raise_deinited_error, these were found by checking the functions found by `-Wmissing-noreturn` and making a case by case decision. However, this dignostic can't be enabled unconditionally as it has false positives, functions we do NOT want to mark as noreturn. Testing performed: built itsybitsy m4, flash size savings 128 bytes. didn't test on hardware as none came on this trip with me.
This was referenced Apr 21, 2025
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Surprisingly this leads to some code size savings on itsybitsym4, even though LTO optimization should have let the compiler deduce (almost) all of this.
When a compiler knows a call can never return, it is possibly able to avoid emitting code, such as saving caller-saved registers to the stack, or doing ANYTHING affter the function returns, explaining why code size savings is possible with this attribute.
With the exception of raise_deinited_error, these were found by checking the functions found by
-Wmissing-noreturnand making a case by case decision. However, this dignostic can't be enabled unconditionally as it has false positives, functions we do NOT want to mark as noreturn.Testing performed: built itsybitsy m4, flash size savings 128 bytes. I didn't test on hardware as none came on this trip with me.