https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78665
Bug ID: 78665
Summary: Unexpected warning about "assuming signed overflow
does not occur when simplifying conditional"
Product: gcc
Version: 6.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: rjones at redhat dot com
Target Milestone: ---
size_t seg_len;
//...
if (seg_len <= 4 || (seg_len & 3) != 0) {
gives:
handle.c: In function 'hivex_open':
handle.c:273:10: error: assuming signed overflow does not occur when
simplifying conditional [-Werror=strict-overflow]
if (seg_len <= 4 || (seg_len & 3) != 0) {
^
The original code is:
https://github.com/libguestfs/hivex/blob/4b024fa031251fbeacb6ecf2821d8d027d59de0d/lib/handle.c#L273
$ gcc --version
gcc (GCC) 6.2.1 20160916 (Red Hat 6.2.1-2)
Copyright (C) 2016 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.
Compilation command is:
libtool: compile: gcc -DHAVE_CONFIG_H -I. -I.. -I../gnulib/lib -I../gnulib/lib
-I. -W -Wabi -Waddress -Waggressive-loop-optimizations -Wall -Wattributes
-Wbad-function-cast -Wbool-compare -Wbuiltin-macro-redefined -Wcast-align
-Wchar-subscripts -Wchkp -Wclobbered -Wcomment -Wcomments -Wcoverage-mismatch
-Wcpp -Wdate-time -Wdeprecated -Wdeprecated-declarations -Wdesignated-init
-Wdisabled-optimization -Wdiscarded-array-qualifiers -Wdiscarded-qualifiers
-Wdiv-by-zero -Wdouble-promotion -Wempty-body -Wendif-labels -Wenum-compare
-Wextra -Wformat-contains-nul -Wformat-extra-args -Wformat-nonliteral
-Wformat-security -Wformat-signedness -Wformat-y2k -Wformat-zero-length
-Wfree-nonheap-object -Wignored-qualifiers -Wimplicit
-Wimplicit-function-declaration -Wimplicit-int -Wincompatible-pointer-types
-Winit-self -Winline -Wint-conversion -Wint-to-pointer-cast
-Winvalid-memory-model -Winvalid-pch -Wlogical-not-parentheses -Wlogical-op
-Wmain -Wmaybe-uninitialized -Wmemset-transposed-args -Wmissing-braces
-Wmissing-declarations -Wmissing-field-initializers -Wmissing-include-dirs
-Wmissing-parameter-type -Wmissing-prototypes -Wmultichar -Wnarrowing
-Wnested-externs -Wnonnull -Wodr -Wold-style-declaration -Wold-style-definition
-Wopenmp-simd -Woverflow -Woverlength-strings -Woverride-init
-Wpacked-bitfield-compat -Wparentheses -Wpointer-arith -Wpointer-sign
-Wpointer-to-int-cast -Wpragmas -Wreturn-local-addr -Wreturn-type
-Wsequence-point -Wshadow -Wshift-count-negative -Wshift-count-overflow
-Wsizeof-array-argument -Wsizeof-pointer-memaccess -Wstack-protector
-Wstrict-aliasing -Wstrict-overflow -Wstrict-prototypes
-Wsuggest-attribute=const -Wsuggest-attribute=format
-Wsuggest-attribute=noreturn -Wsuggest-final-methods -Wsuggest-final-types
-Wswitch -Wswitch-bool -Wswitch-default -Wsync-nand -Wtrampolines -Wtrigraphs
-Wtype-limits -Wuninitialized -Wunknown-pragmas -Wunsafe-loop-optimizations
-Wunused -Wunused-but-set-parameter -Wunused-but-set-variable -Wunused-function
-Wunused-label -Wunused-local-typedefs -Wunused-macros -Wunused-parameter
-Wunused-result -Wunused-value -Wunused-variable -Wvarargs -Wvariadic-macros
-Wvector-operation-performance -Wvolatile-register-var -Wwrite-strings
-Warray-bounds=2 -Wnormalized=nfc -Wno-unused-parameter
-Wno-missing-field-initializers -Wno-logical-op -Wno-array-bounds
-fdiagnostics-show-option -Werror -g -O2 -MT libhivex_la-handle.lo -MD -MP -MF
.deps/libhivex_la-handle.Tpo -c handle.c -fPIC -DPIC -o
.libs/libhivex_la-handle.o
