When compiling the following tiny example .cxx source with "-Wall -O2", I get
spurious warnings:
------------- cut example test.cxx here --------------
extern void function(void * x);
struct A {
long x;
char d[0];
};
void test(A * a) {
function((char *)a - 4); // gcc emits warning, here - why?
}
// ------------
struct B {
char d[0];
};
void test(B * b) {
char * c = (char *)b;
void * v = c-1;
function(v); // gcc emits warning, here - why?
}
------------- cut here --------------
The output of
> gcc -Wall -c test.cxx -O2
is:
/tmp/test.cxx: In function ‘void test(B*)’:
/tmp/test.cxx:22: warning: array subscript is below array bounds
/tmp/test.cxx: In function ‘void test(A*)’:
/tmp/test.cxx:10: warning: array subscript is below array bounds
I have not found a sane way in my non-example, real-world code to avoid those
warnings.
--
Summary: spurious warning "array subscript is below array bounds"
with void* function argument plus -O2
Product: gcc
Version: 4.3.0
Status: UNCONFIRMED
Severity: minor
Priority: P3
Component: c++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: niemayer at isg dot de
GCC build triplet: i686-pc-linux-gnu
GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35593
