Menu
I'm often use do-while(0) construct in my #defines, for the reasons described in this answer. Also I'm trying to use as high as possible warning level from compiler to catch more potential problem and make my code more robust and cross-platform. So I'm typically using -Wall with gcc and /Wall with MSVC.
Unfortunately MSVC complain about do-while(0) construct:
foo.c(36) : warning C4127: conditional expression is constant What should I do about this warning?
Just disable it globally for all files? It does not seems to be good idea for me.
256
They are not errors from the viewpoint of a programming language, but they may be software bugs. However, many compilers can be customized so that their warnings don't stop the compilation process. Warnings must not be ignored. You'd better fix every possible error before starting software testing.
To disable a set of warnings for a given piece of code, you have to start with a “push” pre-processor instruction, then with a disabling instruction for each of the warning you want to suppress, and finish with a “pop” pre-processor instruction.
Compilers emit both erorrs, which prevent your code from compiling at all, and warnings, which indicate a potential problem, but still let your code compile. (Unless you have ask the compiler to treat warnings as errors, such as with the -Werror flag to gcc).
Summary: This warning (C4127) in this particular case is a subtle compiler bug. Feel free to disable it.
In depth:
It was meant to catch situations when logical expression evaluates to a constant in non-obvious situations (such as, if(a==a && a!=a), and somehow, it turned while(true) and other useful constructs into invalid.
Microsoft recommends using for(;;) for infinite loop if you want to have this warning on, and there is no solution for your case. This is one of very few Level-4 warnings my company's development conventions allow to disable.
157
Perhaps your code needs more owls:
do { stuff(); } while (0,0) Or the less photogenic but also less warning producing:
do { stuff(); } while ((void)0,0) If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
