Hi!
The testcases Martin has added recently that contain precision or width
that doesn't fit into int cause UB in the following routine, as 10 * argnum
or that + (*fcp - '0') can result in signed integer overflow.
The following patch just does the computation in UHWI, which we know is
wider than int (I think we don't support 64-bit int hosts yet).
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
Or do you prefer computations in unsigned int?
2019-02-25 Jakub Jelinek <ja...@redhat.com>
PR c/89495
* c-format.c (maybe_read_dollar_number): Compute nargnum in
HOST_WIDE_INT type to avoid overflows and change overflow_flag
checking.
--- gcc/c-family/c-format.c.jj 2019-01-16 09:35:04.565323073 +0100
+++ gcc/c-family/c-format.c 2019-02-25 16:26:07.872810237 +0100
@@ -1268,9 +1268,9 @@ maybe_read_dollar_number (const char **f
overflow_flag = 0;
while (ISDIGIT (*fcp))
{
- int nargnum;
- nargnum = 10 * argnum + (*fcp - '0');
- if (nargnum < 0 || nargnum / 10 != argnum)
+ HOST_WIDE_INT nargnum
+ = HOST_WIDE_INT_UC (10) * argnum + (*fcp - '0');
+ if ((int) nargnum != nargnum)
overflow_flag = 1;
argnum = nargnum;
fcp++;
Jakub
