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