Developer Guide and Reference


Warnings, Errors, and Remarks

This topic describes compiler remarks, warnings, and errors. The compiler sends these messages, along with the erroneous source line, to stderr.


Warning messages report legal but questionable use of C or C++. The compiler displays warnings by default. You can suppress warning messages by specifying an appropriate compiler option. Warnings do not stop translation or linking. Warnings do not interfere with any output files.
The following are some representative warning messages:
  • declaration does not declare anything
  • pointless comparison of unsigned integer with zero
  • possible use of = where == was intended
Some warnings that start with
can be disabled using the negative form of the option
; for example, option
disables option
Additional Warnings
The following Linux* and
options produce additional warnings:
Warn for missing prototypes.
Warn for missing declarations.
Warn for unused variable.
Warn for questionable pointer arithmetic.