https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97049
Bug ID: 97049
Summary: Cryptic warning "__builtin_memmove pointer overflow
between offset ... and size ..." with -m32
Product: gcc
Version: 10.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: officesamurai at gmail dot com
Target Milestone: ---
Created attachment 49216
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=49216&action=edit
The code in question
This looks similar to https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92879 but
this one needs -m32 to reproduce. Also, the warning message doesn't mention the
offending line number which makes it particularly cryptic.
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$ g++-10.2.0 -O2 -m32 -c gcc10_builtin_memmove_exceeds_maximum_obj_size.cpp
In function ‘void foo()’:
cc1plus: warning: ‘void* __builtin_memmove(void*, const void*, unsigned int)’
specified bound 4294967288 exceeds maximum object size 2147483647
[]8;;https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wstringop-overflow=-Wstringop-overflow=]8;;]
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With -Wno-stringop-overflow -Wall another warning is produced:
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$ g++-10.2.0 -O2 -m32 -c gcc10_builtin_memmove_exceeds_maximum_obj_size.cpp
-Wno-stringop-overflow -Wall
In function ‘void foo()’:
cc1plus: warning: ‘void* __builtin_memmove(void*, const void*, unsigned int)’
pointer overflow between offset [0, 1073741831] and size 4294967288
[]8;;https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Warray-bounds-Warray-bounds]8;;]
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Interestingly, if I change the type of 'size' on the line 116 to 'int', the
warnings go away.
The compiler:
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$ g++-10.2.0 -v
Using built-in specs.
COLLECT_GCC=g++-10.2.0
COLLECT_LTO_WRAPPER=/home/brd/soft/gcc-10.2.0/libexec/gcc/x86_64-pc-linux-gnu/10.2.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ./configure --prefix=/home/brd/soft/gcc-10.2.0
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 10.2.0 (GCC)
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