How to set an attribute for all C++ functions without changing code?

Question

I'd like to use the -Wunused-result option in GCC to detect unused/ignored return values in my code. But this requires marking the function declarations either with an attribute, or with attribute specifier sequence.

Doing this by hand could be very time consuming and error-prone. I was wondering if there is a way to tell GCC to set attributes for all functions (or set a default attribute), so that I could use the warning flag.

Well, I tried the option at first, and I got no warnings so I googled what to do, and this answer suggests the attributes. — Machta, Nov 03 '17 at 18:58
yeah sorry, I also just tried it and it seems like the docs arent accurate — 463035818_is_not_an_ai, Nov 03 '17 at 19:02
We cannot use exceptions, so there are a lot of functions that return error codes. I wanted to see where we forgot to handle them. This just seems like something the compiler should be able to do, both warn about the return value and set the attributes... — Machta, Nov 03 '17 at 19:11
in that case that warning alone wont help, because it wont catch cases where a call is `auto x = foo();` but then ignoring `x`, though in combination with the unused variable warning you might be safe — 463035818_is_not_an_ai, Nov 03 '17 at 19:16

score 1 · Answer 1 · answered Nov 03 '17 at 20:08

1

This looks like a job for a GCC plugin. Upstream might also accept a patch which sets the attribute for all subsequent functions using a pragma, but the exact semantics are probably quite tricky for C++.

answered Nov 03 '17 at 20:08

Florian Weimer

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How to set an attribute for all C++ functions without changing code?

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