https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95360
Bug ID: 95360 Summary: inconsistent behaviors at -O0 Product: gcc Version: 10.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: debug Assignee: unassigned at gcc dot gnu.org Reporter: yangyibiao at hust dot edu.cn Target Milestone: --- $ gcc --version gcc (GCC) 10.0.1 20200419 (experimental) Copyright (C) 2020 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. $ gdb --version GNU gdb (GDB) 10.0.50.20200517-git Copyright (C) 2020 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. $ cat small.c unsigned int b,d; static int c[1][2] = {{0, 1}}; int main() { for (; d<1; d++) for (; b<1; b++) c[b][d+1] = 0; return 0; } $ gcc -O0 -g small.c $ gdb -q a.out Reading symbols from a.out... (gdb) b 5 Breakpoint 1 at 0x401106: file small.c, line 5. (gdb) r Starting program: /home/yibiao/Debugger/a.out Breakpoint 1, main () at small.c:5 5 for (; d<1; d++) (gdb) stepi 0x0000000000401154 5 for (; d<1; d++) (gdb) stepi 0x000000000040115a 5 for (; d<1; d++) (gdb) stepi 0x000000000040115c 5 for (; d<1; d++) (gdb) stepi 0x000000000040113b 6 for (; b<1; b++) (gdb) stepi 0x0000000000401141 6 for (; b<1; b++) (gdb) stepi 0x0000000000401143 6 for (; b<1; b++) (gdb) stepi 7 c[b][d+1] = 0; (gdb) /***************************************************** As showed, Line 6 is hit first and then hit Line 7 with stepi. However, when using step, gdb is first hit Line 7 and then hit Line 6. This is an inconsistent behaviors between stepi and step *****************************************************/ $ gdb -q a.out Reading symbols from a.out... (gdb) b main Breakpoint 1 at 0x401106: file small.c, line 5. (gdb) r Starting program: /home/yibiao/Debugger/a.out Breakpoint 1, main () at small.c:5 5 for (; d<1; d++) (gdb) step 7 c[b][d+1] = 0; (gdb) 6 for (; b<1; b++) (gdb) Breakpoint 1, main () at small.c:6 6 for (; b<1; b++) (gdb)