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@c Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
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@c 1999, 2000, 2001, 2003, 2004 Free Software Foundation, Inc.
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@c This is part of the GCC manual.
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@c For copying conditions, see the file gcc.texi.
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@node Bugs
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@chapter Reporting Bugs
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@cindex bugs
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@cindex reporting bugs
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Your bug reports play an essential role in making GCC reliable.
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When you encounter a problem, the first thing to do is to see if it is
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already known. @xref{Trouble}. If it isn't known, then you should
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report the problem.
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@menu
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* Criteria: Bug Criteria. Have you really found a bug?
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* Reporting: Bug Reporting. How to report a bug effectively.
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* Known: Trouble. Known problems.
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* Help: Service. Where to ask for help.
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@end menu
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@node Bug Criteria,Bug Reporting,,Bugs
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@section Have You Found a Bug?
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@cindex bug criteria
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If you are not sure whether you have found a bug, here are some guidelines:
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@itemize @bullet
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@cindex fatal signal
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@cindex core dump
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@item
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If the compiler gets a fatal signal, for any input whatever, that is a
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compiler bug. Reliable compilers never crash.
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@cindex invalid assembly code
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@cindex assembly code, invalid
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@item
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If the compiler produces invalid assembly code, for any input whatever
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(except an @code{asm} statement), that is a compiler bug, unless the
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compiler reports errors (not just warnings) which would ordinarily
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prevent the assembler from being run.
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@cindex undefined behavior
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@cindex undefined function value
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@cindex increment operators
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@item
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If the compiler produces valid assembly code that does not correctly
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execute the input source code, that is a compiler bug.
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However, you must double-check to make sure, because you may have a
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program whose behavior is undefined, which happened by chance to give
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the desired results with another C or C++ compiler.
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For example, in many nonoptimizing compilers, you can write @samp{x;}
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at the end of a function instead of @samp{return x;}, with the same
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results. But the value of the function is undefined if @code{return}
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is omitted; it is not a bug when GCC produces different results.
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Problems often result from expressions with two increment operators,
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as in @code{f (*p++, *p++)}. Your previous compiler might have
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interpreted that expression the way you intended; GCC might
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interpret it another way. Neither compiler is wrong. The bug is
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in your code.
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After you have localized the error to a single source line, it should
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be easy to check for these things. If your program is correct and
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well defined, you have found a compiler bug.
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@item
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If the compiler produces an error message for valid input, that is a
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compiler bug.
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@cindex invalid input
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@item
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If the compiler does not produce an error message for invalid input,
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that is a compiler bug. However, you should note that your idea of
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``invalid input'' might be someone else's idea of ``an extension'' or
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``support for traditional practice''.
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@item
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If you are an experienced user of one of the languages GCC supports, your
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suggestions for improvement of GCC are welcome in any case.
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@end itemize
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@node Bug Reporting,,Bug Criteria,Bugs
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@section How and where to Report Bugs
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@cindex compiler bugs, reporting
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Bugs should be reported to the GCC bug database. Please refer to
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@uref{http://gcc.gnu.org/bugs.html} for up-to-date instructions how to
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submit bug reports. Copies of this file in HTML (@file{bugs.html}) and
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plain text (@file{BUGS}) are also part of GCC releases.
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