Wextra

Wextra is a compiler warning option available in GCC and Clang designed to enable a broader set of diagnostic messages than the basic -Wall warnings. It aims to help developers identify potential issues that might not be covered by -Wall.

Historically, -Wextra has been part of GCC's and Clang's warning controls to provide additional checks beyond -Wall. Its warnings cover a broader range of potential issues, but they can be more verbose.

Typical usage is to compile with -Wall -Wextra, and often -Werror to treat warnings as errors. It is commonly paired with -Wpedantic to enforce strict conformance to language standards.

Wextra can surface warnings about unused parameters, suspicious type conversions, or inconsistent signedness in comparisons, as examples of the kinds of messages it can produce. The exact set of warnings depends on the compiler and language standard in use.

Wextra is supported by both GCC and Clang and behaves predictably across them, though warning semantics vary by version and standard. Enabling -Wextra may require code changes to fix warnings and can be noisy for large or legacy codebases.

Related options include -Wall, -Wpedantic, -Wconversion, and -Werror.