[PATCH] c: Fix ICEs with -fsanitize=pointer-{subtract,compare} [PR119582]

[Jakub Jelinek]

Hi!

The following testcase ICEs because c_fully_fold isn't performed on the
arguments of __sanitizer_ptr_{sub,cmp} builtins and so e.g.
C_MAYBE_CONST_EXPR can leak into the gimplifier where it ICEs.

Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
trunk?

2025-04-02  Jakub Jelinek  <ja...@redhat.com>

        PR c/119582
        * c-typeck.cc (pointer_diff, build_binary_op): Call c_fully_fold on
        __sanitizer_ptr_sub or __sanitizer_ptr_cmp arguments.

        * gcc.dg/asan/pr119582.c: New test.

--- gcc/c/c-typeck.cc.jj        2025-03-27 09:29:36.953576540 +0100
+++ gcc/c/c-typeck.cc   2025-04-02 15:04:47.103495567 +0200
@@ -4824,8 +4824,8 @@ pointer_diff (location_t loc, tree op0,
   if (current_function_decl != NULL_TREE
       && sanitize_flags_p (SANITIZE_POINTER_SUBTRACT))
     {
-      op0 = save_expr (op0);
-      op1 = save_expr (op1);
+      op0 = save_expr (c_fully_fold (op0, false, NULL));
+      op1 = save_expr (c_fully_fold (op1, false, NULL));
 
       tree tt = builtin_decl_explicit (BUILT_IN_ASAN_POINTER_SUBTRACT);
       *instrument_expr = build_call_expr_loc (loc, tt, 2, op0, op1);
@@ -14455,8 +14455,8 @@ build_binary_op (location_t location, en
          && current_function_decl != NULL_TREE
          && sanitize_flags_p (SANITIZE_POINTER_COMPARE))
        {
-         op0 = save_expr (op0);
-         op1 = save_expr (op1);
+         op0 = save_expr (c_fully_fold (op0, false, NULL));
+         op1 = save_expr (c_fully_fold (op1, false, NULL));
 
          tree tt = builtin_decl_explicit (BUILT_IN_ASAN_POINTER_COMPARE);
          instrument_expr = build_call_expr_loc (location, tt, 2, op0, op1);
--- gcc/testsuite/gcc.dg/asan/pr119582.c.jj     2025-04-02 15:11:22.351048509 
+0200
+++ gcc/testsuite/gcc.dg/asan/pr119582.c        2025-04-02 15:11:57.600561599 
+0200
@@ -0,0 +1,23 @@
+/* PR c/119582 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fsanitize=address,pointer-subtract,pointer-compare" } */
+
+const char v;
+typedef __PTRDIFF_TYPE__ ptrdiff_t;
+char a;
+const ptrdiff_t p = &a + 1 - &a;
+const int q = (&a + 1) != &a;
+
+ptrdiff_t
+foo (void)
+{
+  char b;
+  return &b + (v != '\n') - &b;
+}
+
+int
+bar (void)
+{
+  char b;
+  return (&b + (v != '\n')) != &b;
+}

        Jakub