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From: "bernie at codewiz dot org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/105438] New: Incorrect array-bounds warning with array size carried over from a previous template instantiation Date: Sat, 30 Apr 2022 08:24:55 +0000 [thread overview] Message-ID: <bug-105438-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105438 Bug ID: 105438 Summary: Incorrect array-bounds warning with array size carried over from a previous template instantiation Product: gcc Version: 11.3.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: bernie at codewiz dot org Target Milestone: --- Minified testcase (almost every line is necessary to reproduce): ``` /* g++ -Warray-bounds -O2 repro.cc */ int longer[7] = {}; int shorter[2] = {}; int out[10] = {}; template <int N> void configure(const int(&in)[N], const int nrows = N) { if (nrows <= 10) { for (int i = 0; i < nrows; i++) { out[i] = in[i]; } } } int main() { configure(longer); configure(shorter); } ``` Output: ``` $ g++ -Warray-bounds -O2 repro.cc repro.cc: In function 'int main()': repro.cc:13:24: warning: array subscript 'const int [7][0]' is partly outside array bounds of 'int [2]' [-Warray-bounds] 13 | out[i] = in[i]; | ~~^ repro.cc:3:5: note: while referencing 'shorter' 3 | int shorter[2] = {}; | ^~~~~~~ repro.cc:13:24: warning: array subscript 'const int [7][0]' is partly outside array bounds of 'int [2]' [-Warray-bounds] 13 | out[i] = in[i]; | ~~^ repro.cc:3:5: note: while referencing 'shorter' 3 | int shorter[2] = {}; | ^~~~~~~ ``` Static analysis appears to be using the length of the longer array for the call using the shorter array. The warning disappears by: * commenting out the first call to configure() suppresses the warning * swapping the two calls to configure() * commenting out if statement also eliminates the warning * making longer and shorter the same size * using N as loop counter instead of nrows
next reply other threads:[~2022-04-30 8:24 UTC|newest] Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-04-30 8:24 bernie at codewiz dot org [this message] 2022-04-30 8:27 ` [Bug c++/105438] " bernie at codewiz dot org 2022-05-02 6:05 ` bernie at codewiz dot org 2022-05-02 6:07 ` bernie at codewiz dot org 2022-05-02 6:11 ` bernie at codewiz dot org 2022-05-02 6:54 ` [Bug ipa/105438] " rguenth at gcc dot gnu.org 2022-05-02 6:57 ` [Bug ipa/105438] [11/12/13 Regression] " pinskia at gcc dot gnu.org 2022-05-03 12:27 ` [Bug ipa/105438] [11/12/13 Regression] Incorrect array-bounds warning with array size carried over from a previous template instantiation since r11-4987-g602c6cfc79ce4ae6 since r11-4987-g602c6cfc79ce4ae6 marxin at gcc dot gnu.org 2022-05-03 12:42 ` marxin at gcc dot gnu.org 2022-07-26 11:39 ` [Bug ipa/105438] [11/12/13 Regression] Incorrect array-bounds warning with array size carried over from a previous template instantiation " rguenth at gcc dot gnu.org 2023-01-22 0:55 ` bernie at codewiz dot org 2023-02-09 11:37 ` marxin at gcc dot gnu.org 2023-05-29 10:06 ` [Bug ipa/105438] [11/12/13/14 " jakub at gcc dot gnu.org 2023-07-20 7:23 ` bernie at codewiz dot org 2023-07-27 9:22 ` rguenth at gcc dot gnu.org
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