gcc.info: Bug Criteria
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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 a compiler bug. Reliable compilers never crash.
* If the compiler produces invalid assembly code, for any input
whatever (except an `asm' statement), that is a compiler bug,
unless the compiler reports errors (not just warnings) which would
ordinarily prevent the assembler from being run.
* If the compiler produces valid assembly code that does not
correctly execute the input source code, that is a compiler bug.
However, you must double-check to make sure, because you may have
run into an incompatibility between GNU C and traditional C (*note
Incompatibilities::.). These incompatibilities might be considered
bugs, but they are inescapable consequences of valuable features.
Or you may have a program whose behavior is undefined, which
happened by chance to give the desired results with another C or
C++ compiler.
For example, in many nonoptimizing compilers, you can write `x;'
at the end of a function instead of `return x;', with the same
results. But the value of the function is undefined if `return'
is omitted; it is not a bug when GCC produces different results.
Problems often result from expressions with two increment
operators, as in `f (*p++, *p++)'. Your previous compiler might
have interpreted that expression the way you intended; GCC might
interpret it another way. Neither compiler is wrong. The bug is
in your code.
After you have localized the error to a single source line, it
should be easy to check for these things. If your program is
correct and well defined, you have found a compiler bug.
* If the compiler produces an error message for valid input, that is
a compiler 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 my idea of "an extension" or
"support for traditional practice".
* If you are an experienced user of C or C++ (or Fortran or
Objective-C) compilers, your suggestions for improvement of GCC
are welcome in any case.
Created Wed Sep 1 16:42:21 2004 on bee with info_to_html version 0.9.6.