1@c Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
2@c 1999, 2000, 2001, 2003, 2004, 2007 Free Software Foundation, Inc.
3@c This is part of the GCC manual.
4@c For copying conditions, see the file gcc.texi.
5
6@node Bugs
7@chapter Reporting Bugs
8@cindex bugs
9@cindex reporting bugs
10
11Your bug reports play an essential role in making GCC reliable.
12
13When you encounter a problem, the first thing to do is to see if it is
14already known.  @xref{Trouble}.  If it isn't known, then you should
15report the problem.
16
17@menu
18* Criteria:  Bug Criteria.   Have you really found a bug?
19* Reporting: Bug Reporting.  How to report a bug effectively.
20* Known: Trouble.            Known problems.
21* Help: Service.             Where to ask for help.
22@end menu
23
24@node Bug Criteria,Bug Reporting,,Bugs
25@section Have You Found a Bug?
26@cindex bug criteria
27
28If you are not sure whether you have found a bug, here are some guidelines:
29
30@itemize @bullet
31@cindex fatal signal
32@cindex core dump
33@item
34If the compiler gets a fatal signal, for any input whatever, that is a
35compiler bug.  Reliable compilers never crash.
36
37@cindex invalid assembly code
38@cindex assembly code, invalid
39@item
40If the compiler produces invalid assembly code, for any input whatever
41(except an @code{asm} statement), that is a compiler bug, unless the
42compiler reports errors (not just warnings) which would ordinarily
43prevent the assembler from being run.
44
45@cindex undefined behavior
46@cindex undefined function value
47@cindex increment operators
48@item
49If the compiler produces valid assembly code that does not correctly
50execute the input source code, that is a compiler bug.
51
52However, you must double-check to make sure, because you may have a
53program whose behavior is undefined, which happened by chance to give
54the desired results with another C or C++ compiler.
55
56For example, in many nonoptimizing compilers, you can write @samp{x;}
57at the end of a function instead of @samp{return x;}, with the same
58results.  But the value of the function is undefined if @code{return}
59is omitted; it is not a bug when GCC produces different results.
60
61Problems often result from expressions with two increment operators,
62as in @code{f (*p++, *p++)}.  Your previous compiler might have
63interpreted that expression the way you intended; GCC might
64interpret it another way.  Neither compiler is wrong.  The bug is
65in your code.
66
67After you have localized the error to a single source line, it should
68be easy to check for these things.  If your program is correct and
69well defined, you have found a compiler bug.
70
71@item
72If the compiler produces an error message for valid input, that is a
73compiler bug.
74
75@cindex invalid input
76@item
77If the compiler does not produce an error message for invalid input,
78that is a compiler bug.  However, you should note that your idea of
79``invalid input'' might be someone else's idea of ``an extension'' or
80``support for traditional practice''.
81
82@item
83If you are an experienced user of one of the languages GCC supports, your
84suggestions for improvement of GCC are welcome in any case.
85@end itemize
86
87@node Bug Reporting,,Bug Criteria,Bugs
88@section How and where to Report Bugs
89@cindex compiler bugs, reporting
90
91Bugs should be reported to the bug database at @value{BUGURL}.
92