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Comment by NotPaidToPost | Hacker News Reader

> It's a warning not an error.

Many build environments are set to treat all warnings as errors.

The point is that 2^32 is a perfectly compliant C expression that is neither misleading nor ambiguous, and that also won't create any variable overflow. It uses ^ exactly as intended. Why should the compiler complain? Why should I get a warning/error when following the spec to the letter?

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Like it or not, there are already tons of lint-like warnings in GCC [1] and clang [2]. Many (uh, most?) of them are not required by the C/C++ standards (which by the way have their own requirements for diagnostic messages).

[1] https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html

[2] https://clang.llvm.org/docs/DiagnosticsReference.html

Plenty of valid expressions generate warnings. A frequent gotcha is `=` in boolean contexts. Warnings are justified, and can normally be avoided with a little bit more lexical work (e.g. an extra set of parentheses). The upside is large and the downside is miniscule.

Isn't that pretty much the definition of a warning? An expression that is technically valid, but probably a mistake. If something wasn't a valid expression, it would be a compiler error, not a warning.

Usually, yes. C is weird because undefined behavior is illegal, can sometimes be detected statically, and yet will not produce an error. So sometimes you get warnings for invalid yet error-free code. It’s a strange language.

Environments where the decision has been made that error-prone, misleading and ambiguous statements should not be allowed typically are those where warning are treated as errors.

A new type of misleading and error-prone statement has been found, so it seems entirely reasonable that this is added to that list.

This seems to be the entire intent of compiler warnings (these days anyway)

Heuristics like this are important because humans are not machines. If you run into a warning in one of these situations, they are usually rectified by changing the statement slightly. Worst case scenario you can #pragma push and pop the warning.

The compiler should complain because it's overwhelmingly likely to be a mistake.

You can turn specific warnings off. You can also usually disable them inline. There are very common ways to deal with false positive warnings.

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