1 @c Copyright (C) 1988-2023 Free Software Foundation, Inc.
2 @c This is part of the GCC manual.
3 @c For copying conditions, see the file gcc.texi.
6 @chapter Reporting Bugs
10 Your bug reports play an essential role in making GCC reliable.
12 When you encounter a problem, the first thing to do is to see if it is
13 already known. @xref{Trouble}. If it isn't known, then you should
17 * Criteria: Bug Criteria. Have you really found a bug?
18 * Reporting: Bug Reporting. How to report a bug effectively.
22 @section Have You Found a Bug?
25 If you are not sure whether you have found a bug, here are some guidelines:
31 If the compiler gets a fatal signal, for any input whatever, that is a
32 compiler bug. Reliable compilers never crash.
34 @cindex invalid assembly code
35 @cindex assembly code, invalid
37 If the compiler produces invalid assembly code, for any input whatever
38 (except an @code{asm} statement), that is a compiler bug, unless the
39 compiler reports errors (not just warnings) which would ordinarily
40 prevent the assembler from being run.
42 @cindex undefined behavior
43 @cindex undefined function value
44 @cindex increment operators
46 If the compiler produces valid assembly code that does not correctly
47 execute the input source code, that is a compiler bug.
49 However, you must double-check to make sure, because you may have a
50 program whose behavior is undefined, which happened by chance to give
51 the desired results with another C or C++ compiler.
53 For example, in many nonoptimizing compilers, you can write @samp{x;}
54 at the end of a function instead of @samp{return x;}, with the same
55 results. But the value of the function is undefined if @code{return}
56 is omitted; it is not a bug when GCC produces different results.
58 Problems often result from expressions with two increment operators,
59 as in @code{f (*p++, *p++)}. Your previous compiler might have
60 interpreted that expression the way you intended; GCC might
61 interpret it another way. Neither compiler is wrong. The bug is
64 After you have localized the error to a single source line, it should
65 be easy to check for these things. If your program is correct and
66 well defined, you have found a compiler bug.
69 If the compiler produces an error message for valid input, that is a
74 If the compiler does not produce an error message for invalid input,
75 that is a compiler bug. However, you should note that your idea of
76 ``invalid input'' might be someone else's idea of ``an extension'' or
77 ``support for traditional practice''.
80 If you are an experienced user of one of the languages GCC supports, your
81 suggestions for improvement of GCC are welcome in any case.
85 @section How and Where to Report Bugs
86 @cindex compiler bugs, reporting
88 Bugs should be reported to the bug database at @value{BUGURL}.