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16.1 Have You Found a Bug? ¶

If you are not sure whether you have found a bug, here are some guidelines:

• If the compiler gets a fatal signal, for any input whatever, that is acompiler bug. Reliable compilers never crash.
• If the compiler produces invalid assembly code, for any input whatever(except anasm statement), that is a compiler bug, unless thecompiler reports errors (not just warnings) which would ordinarilyprevent the assembler from being run.
• If the compiler produces valid assembly code that does not correctlyexecute the input source code, that is a compiler bug.

  However, you must double-check to make sure, because you may have aprogram whose behavior is undefined, which happened by chance to givethe desired results with another C or C++ compiler.

  Problems often result from expressions with two increment operators,as inf (*p++, *p++). Your previous compiler might haveinterpreted that expression the way you intended; GCC mightinterpret it another way. Neither compiler is wrong. The bug isin your code.

  After you have localized the error to a single source line, it shouldbe easy to check for these things. If your program is correct andwell defined, you have found a compiler bug.

• If the compiler produces an error message for valid input, that is acompiler bug.
• If the compiler does not produce an error message for invalid input,that is a compiler bug. However, you should note that your idea of“invalid input” might be someone else’s idea of “an extension” or“support for traditional practice”.
• If you are an experienced user of one of the languages GCC supports, yoursuggestions for improvement of GCC are welcome in any case.

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