On 11/23/18 11:24 PM, Marc Glisse wrote:
On Fri, 23 Nov 2018, NightStrike wrote:
What would cause gcc (8.1.0) to lose line numbers when printing out a
warning?
$ gcc -O3 -g -c file.c -o file.o (followed by tons of -I's)
./file.h: In function 'fcn':
cc1: warning: '__builtin_memset' writing 72 bytes into a region of
size 52 overflows the destination [-Wstringop-overflow=]
Note that the function is pretty large, and there's no direct calls to
memset, so I'm guessing some optimization is converting a loop to a
memset or something.
I don't have a reduced case yet... I've got 30k lines I'm trying to
auto-shrink down.
int a[13];
void f(){
for(int i=0;i<18;++i)
a[i]=0;
}
$ gcc-snapshot a.c -O3 -S -Wno-aggressive-loop-optimizations
a.c: In function 'f':
cc1: warning: '__builtin_memset' writing 72 bytes into a region of size
52 overflows the destination [-Wstringop-overflow=]
This call to memset is generated in generate_memset_builtin in
tree-loop-distribution.c. One could try calling gimple_set_location
using for instance find_loop_location, or the location of the write.
There are other instances where this problem can come up with
other warnings as well but I don't think we have test cases for
any of them in Bugzilla. Can one of you please open a bug for
this one so we can track and fix it?
Thanks
Martin
