https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90758
Bug ID: 90758 Summary: out of bounds warning with -O3 Product: gcc Version: 7.4.1 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c Assignee: unassigned at gcc dot gnu.org Reporter: pmatos at gcc dot gnu.org Target Milestone: --- Created attachment 46455 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=46455&action=edit testcase There's a bad out of bounds warning in gcc7 line which seems to be fixed in gcc8 and later which only occurs with -O3. With the attached file and the command line: /home/pmatos/Projects/gcc-build/gcc/cc1 -fpreprocessed vfasl.i -quiet -dumpbase vfasl.i -m64 -msse2 -mtune=generic -march=x86-64 -auxbase vfasl -O3 -Wpointer-arith -Wextra -Werror -Wimplicit-fallthrough=0 -Wall -version -o /tmp/ccYGabNR.s GNU C11 (GCC) version 7.4.1 20190605 (x86_64-pc-linux-gnu) compiled by GNU C version 8.2.1 20181127, GMP version 6.1.2, MPFR version 4.0.2, MPC version 1.1.0, isl version none GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096 GNU C11 (GCC) version 7.4.1 20190605 (x86_64-pc-linux-gnu) compiled by GNU C version 8.2.1 20181127, GMP version 6.1.2, MPFR version 4.0.2, MPC version 1.1.0, isl version none GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096 Compiler executable checksum: 4c52f0564d8672c9a189665c732e246d vfasl.i: In function ‘l’: vfasl.i:25:14: error: array subscript is above array bounds [-Werror=array-bounds] ay = at[ax]; ~~^~~~ vfasl.i: In function ‘j’: vfasl.i:42:11: error: ‘n’ is used uninitialized in this function [-Werror=uninitialized] *(a *)0 = n; ~~~~~~~~^~~ vfasl.i:45:3: note: ‘n’ was declared here a j(ac *m, a n) { return o(m, n); } ^ cc1: all warnings being treated as errors