gcc: Bug Criteria

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1 14.1 Have You Found a Bug?
1 ==========================
1 
1 If you are not sure whether you have found a bug, here are some
1 guidelines:
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1    * If the compiler gets a fatal signal, for any input whatever, that
1      is a compiler bug.  Reliable compilers never crash.
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1    * If the compiler produces invalid assembly code, for any input
1      whatever (except an 'asm' statement), that is a compiler bug,
1      unless the compiler reports errors (not just warnings) which would
1      ordinarily prevent the assembler from being run.
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1    * If the compiler produces valid assembly code that does not
1      correctly execute the input source code, that is a compiler bug.
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1      However, you must double-check to make sure, because you may have a
1      program whose behavior is undefined, which happened by chance to
1      give the desired results with another C or C++ compiler.
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1      For example, in many nonoptimizing compilers, you can write 'x;' at
1      the end of a function instead of 'return x;', with the same
1      results.  But the value of the function is undefined if 'return' is
1      omitted; it is not a bug when GCC produces different results.
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1      Problems often result from expressions with two increment
1      operators, as in 'f (*p++, *p++)'.  Your previous compiler might
1      have interpreted that expression the way you intended; GCC might
1      interpret it another way.  Neither compiler is wrong.  The bug is
1      in your code.
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1      After you have localized the error to a single source line, it
1      should be easy to check for these things.  If your program is
1      correct and well defined, you have found a compiler bug.
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1    * If the compiler produces an error message for valid input, that is
1      a compiler bug.
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1    * If the compiler does not produce an error message for invalid
1      input, that is a compiler bug.  However, you should note that your
1      idea of "invalid input" might be someone else's idea of "an
1      extension" or "support for traditional practice".
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1    * If you are an experienced user of one of the languages GCC
1      supports, your suggestions for improvement of GCC are welcome in
1      any case.
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