https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106626
--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by David Malcolm <dmalc...@gcc.gnu.org>: https://gcc.gnu.org/g:7c655699ed51b0c987e5472767db48b19044ae05 commit r13-4427-g7c655699ed51b0c987e5472767db48b19044ae05 Author: David Malcolm <dmalc...@redhat.com> Date: Wed Nov 30 21:26:42 2022 -0500 analyzer: add note about valid subscripts [PR106626] Consider -fanalyzer on: #include <stdint.h> int32_t arr[10]; void int_arr_write_element_after_end_off_by_one(int32_t x) { arr[10] = x; } Trunk x86_64: https://godbolt.org/z/17zn3qYY4 Currently we emit: <source>: In function 'int_arr_write_element_after_end_off_by_one': <source>:7:11: warning: buffer overflow [CWE-787] [-Wanalyzer-out-of-bounds] 7 | arr[10] = x; | ~~~~~~~~^~~ event 1 | | 3 | int32_t arr[10]; | | ^~~ | | | | | (1) capacity is 40 bytes | +--> 'int_arr_write_element_after_end_off_by_one': events 2-3 | | 5 | void int_arr_write_element_after_end_off_by_one(int32_t x) | | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | | | | | (2) entry to 'int_arr_write_element_after_end_off_by_one' | 6 | { | 7 | arr[10] = x; | | ~~~~~~~~~~~ | | | | | (3) out-of-bounds write from byte 40 till byte 43 but 'arr' ends at byte 40 | <source>:7:11: note: write of 4 bytes to beyond the end of 'arr' 7 | arr[10] = x; | ~~~~~~~~^~~ This is worded in terms of bytes, due to the way -Wanalyzer-out-of-bounds is implemented, but this isn't what the user wrote. This patch tries to get closer to the user's code by adding a note about array bounds when we're referring to an array. In the above example it adds this trailing note: note: valid subscripts for 'arr' are '[0]' to '[9]' gcc/analyzer/ChangeLog: PR analyzer/106626 * bounds-checking.cc (out_of_bounds::maybe_describe_array_bounds): New. (buffer_overflow::emit): Call maybe_describe_array_bounds. (buffer_overread::emit): Likewise. (buffer_underflow::emit): Likewise. (buffer_underread::emit): Likewise. gcc/testsuite/ChangeLog: PR analyzer/106626 * gcc.dg/analyzer/call-summaries-2.c: Add dg-message for expected note about valid indexes. * gcc.dg/analyzer/out-of-bounds-1.c: Likewise, fixing up existing dg-message directives. * gcc.dg/analyzer/out-of-bounds-write-char-arr.c: Likewise. * gcc.dg/analyzer/out-of-bounds-write-int-arr.c: Likewise. Signed-off-by: David Malcolm <dmalc...@redhat.com>
