Hi!
As mentioned in the PR, LOCATION_LINE is represented in an int,
and while we have -pedantic diagnostics (and -pedantic-error error)
for too large #line, we can still overflow into negative line
numbers up to -2 and -1. We could overflow to that even with valid
source if it says has #line 2147483640 and then just has
2G+ lines after it.
Now, the ICE is because assign_discriminator{,s} uses a hash_map
with int_hash <int64_t, -1, -2>, so values -2 and -1 are reserved
for deleted and empty entries. We just need to make sure those aren't
valid. One possible fix would be just that
- discrim_entry &e = map.get_or_insert (LOCATION_LINE (loc), &existed);
+ discrim_entry &e
+ = map.get_or_insert ((unsigned) LOCATION_LINE (loc), &existed);
by adding unsigned cast when the key is signed 64-bit, it will never
be -1 or -2.
But I think that is wasteful, discrim_entry is a struct with 2 unsigned
non-static data members, so for lines which can only be 0 to 0xffffffff
(sure, with wrap-around), I think just using a hash_map with 96bit elts
is better than 128bit.
So, the following patch just doesn't assign any discriminators for lines
-1U and -2U, I think that is fine, normal programs never do that.
Another possibility would be to handle lines -1U and -2U as if it was say
-3U.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2025-09-02 Jakub Jelinek <ja...@redhat.com>
PR middle-end/121663
* tree-cfg.cc (assign_discriminator): Change map argument type
from hash_map with int_hash <int64_t, -1, -2> to one with
int_hash <unsigned, -1U, -2U>. Cast LOCATION_LINE to unsigned.
Return early for (unsigned) LOCATION_LINE above -3U.
(assign_discriminators): Change map type from hash_map with
int_hash <int64_t, -1, -2> to one with int_hash <unsigned, -1U, -2U>.
* gcc.dg/pr121663.c: New test.
--- gcc/tree-cfg.cc.jj 2025-08-23 15:00:04.928779140 +0200
+++ gcc/tree-cfg.cc 2025-09-01 15:56:17.711505423 +0200
@@ -1095,10 +1095,14 @@ struct discrim_entry
location_t
assign_discriminator (location_t loc, unsigned int bb_id,
- hash_map<int_hash <int64_t, -1, -2>, discrim_entry> &map)
+ hash_map<int_hash <unsigned, -1U, -2U>,
+ discrim_entry> &map)
{
bool existed;
- discrim_entry &e = map.get_or_insert (LOCATION_LINE (loc), &existed);
+ if ((unsigned) LOCATION_LINE (loc) >= -2U)
+ return loc;
+ discrim_entry &e
+ = map.get_or_insert ((unsigned) LOCATION_LINE (loc), &existed);
gcc_checking_assert (!has_discriminator (loc));
if (!existed)
{
@@ -1121,7 +1125,7 @@ assign_discriminator (location_t loc, un
static void
assign_discriminators (void)
{
- hash_map<int_hash <int64_t, -1, -2>, discrim_entry> map (13);
+ hash_map<int_hash <unsigned, -1U, -2U>, discrim_entry> map (13);
unsigned int bb_id = 0;
basic_block bb;
FOR_EACH_BB_FN (bb, cfun)
--- gcc/testsuite/gcc.dg/pr121663.c.jj 2025-09-01 16:09:17.623363163 +0200
+++ gcc/testsuite/gcc.dg/pr121663.c 2025-09-01 16:09:41.325054619 +0200
@@ -0,0 +1,9 @@
+/* PR middle-end/121663 */
+/* { dg-do compile } */
+/* { dg-options "" } */
+
+void
+foo (void)
+{
+#line 4294967295
+}
Jakub
