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Comments on Scheme for cross-platform warning control?

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Scheme for cross-platform warning control?

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tl;dr I'd like to learn a compact, cross-compiler way of selectively suppressing compiler warnings.


Consider the case where you really mean to make an exact floating-point comparison using ==, or the case where you capture a return value that you don't use in production but want to assert on in debug.

If you are running your compiler with a highly level of feedback you're going to get a warnings from the first all the time and from the second when performing a release build.

Now, most compilers have a way to annotate a symbol to let the compiler know you're aware of the situation (for instance __attribute__((unused)) in gcc), and various pre-processor pragmas to adjust the compilation envrionment. But we have three compilers to worry about (gcc and msvc for actually building the code on different target platforms and clang as a linter on both).

In some places we actually have painfully heavy and intrusive pre-processor constructs like:

#if defined(_MSC_VER)
#pragma warnings(push)
#pramga warnings(disable : 123456)
#elif defined(__clang__)
#pragma clang diagnostic push
#pramga clang diagnostic ignored "-Wluggage-combination"
#elif defined(__GNUC__)
#pragma GCC diagnostic push
#pramga GCC diagnostic ignored "-Wcode-for-my-luggage"
#endif

    // Offending line(s) of code

#if defined(_MSC_VER)
#pragma warnings(pop)
#elif defined(__clang__)
#pragma clang diagnostic pop
#elif defined(__GNUC__)
#pragma GCC diagnostic pop
#endif

Which, though ugly as sin, works and doesn't cause too much nausea if it occurs once in a low-level module that you don't touch often.

But I feel that it should be easier and neater.

Anyone have a working solution?

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1 comment thread

General comments (4 comments)
General comments
Lundin‭ wrote almost 4 years ago

Compiler warnings are... compiler-specific :) You should probably manage these through different builds per compiler, if possible, keeping everything in IDE project settings or make files. Asserts in particular should be handled with debug vs release builds. As for exact floating point comparison, consider using memcmp instead of ==.

dmckee‭ wrote almost 4 years ago

@Lundin Using memcmp changes the semantics (NaNs can compare equal...) so you need to think about what you intend. We actually have a namespace where we define various classes of floating point comparisons (and use the abhorrent mess above in the implementation for fp::exactlyEqual) so that the code can express intent in words.

Lundin‭ wrote almost 4 years ago

@dmckee Nan is going to be a special case no matter what you do.

Ringi‭ wrote almost 4 years ago

One option I used in the past is a custom preprocessor that the building system calls before passing the resulting file to the compiler.