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Comments on Should I cast to (void) when I do not use the return value

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Should I cast to (void) when I do not use the return value

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I saw at least one compiler (Codewarrior for HC12) warn me if I use a function without using it's return value. Other compilers (clang/gcc) do not issue a warning though, even when using the std=90 argument.

So should I generally cast the unused return value of a function to (void)?

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I saw at least one compiler (Codewarrior for HC12) warn me if I use a function without using it's return value. [...]

Ye, for that's the right choice.

[...] Other compilers (clang/gcc) do not issue a warning though, even when using the std=90 argument.

It will, provided that the function is correctly marked warn_unused_result (https://gcc.gnu.org/onlinedocs/gcc-4.6.0/gcc/Warning-Options.html). The software is should be edited as making results use mandatory. Else functions are to return void.

So should I generally cast the unused return value of a function to (void)?

Never. The returned value is always meaningful and has always to be treated.

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General comments (3 comments)
General comments
Kami‭ wrote over 3 years ago

I highly doubt your last statement. A function like strcpy has no meaningful return value, it is just there to be able to chain function calls afaik.

Lundin‭ wrote over 3 years ago · edited over 3 years ago

warn_unused_result is pretty useless, since it doesn't work unless you pollute your code with non-standard __attribute__ crap. There is no reason why they can't check for it in standard C.

Lundin‭ wrote over 3 years ago

"Never. The returned value is always meaningful and has always to be treated." That kind of depends on how the function is written, yeah? Take strcpy as one example of a function with an often useless return value.