https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83688
Bug ID: 83688
Summary: Please check if buffers may overlap when copying
strings
Product: gcc
Version: 8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: bugzi...@poradnik-webmastera.com
Target Milestone: ---
Functions like strcpy internally use memcpy to copy data. This may cause
problems when someone will try to use them to move string in buffer, e.g. to
strip prefix. gcc is able to detect if overlapping buffers are used with
memcpy. Please add similar diagnostics to strcpy/sprintf functions too.
[code]
#include <string.h>
#include <stdio.h>
char buf[20];
void test()
{
strcpy(buf, buf+5);
memcpy(buf, buf+5, strlen(buf+5)+1);
snprintf(buf, sizeof(buf), "%s", buf+5);
memcpy(buf, buf+5, 10);
}
[/code]
[out]
$ g++ -c -o test.o test.cc -O3 -Wall -Wextra -Wformat-overflow
-Wformat-truncation -Wstringop-overflow=2 -Wstringop-truncation
test.cc: In function ‘void test()’:
test.cc:13:11: warning: ‘void* memcpy(void*, const void*, size_t)’ accessing 10
bytes at offsets 0 and 5 overlaps 5 bytes at offset 5 [-Wrestrict]
memcpy(buf, buf+5, 10);
~~~~~~^~~~~~~~~~~~~~~~
$ g++ --version
g++ (GCC) 8.0.0 20171231 (experimental)
[/out]
