[gcc r16-7077] C: Do not warn for calls to .ACCESS_WITH_SIZE when -Wbad-function-cast is specified [PR123500]

[Qing Zhao]

https://gcc.gnu.org/g:078b0a2be260ccb2c118865058e75ae038fc1949

commit r16-7077-g078b0a2be260ccb2c118865058e75ae038fc1949
Author: Qing Zhao <qing.zhao@oracle.com>
Date:   Mon Jan 26 20:22:43 2026 +0000

    C: Do not warn for calls to .ACCESS_WITH_SIZE when -Wbad-function-cast is specified [PR123500]
    
    For the following source code:
    
    (uintptr_t)b->ptr;
    
    when b->ptr has an counted_by annotation, the IR for this pointer reference
    is changed to a call to .ACCESS_WITH_SIZE as:
    
    (uintptr_t).ACCESS_WITH_SIZE (b->ptr, &b->len, 0B, 1);
    
    As a result, the following code in the routine "build_c_cast" is invoked:
    
     7455       if (TREE_CODE (value) == CALL_EXPR
     7456           && TREE_CODE (type) != TREE_CODE (otype))
     7457         warning_at (loc, OPT_Wbad_function_cast,
     7458                     "cast from function call of type %qT "
     7459                     "to non-matching type %qT", otype, type);
     7460
    
    It's obviously that C FE should exclude the call to .ACCESS_WITH_SIZE from
    issuing such warning.
    
            PR c/123500
    
    gcc/c/ChangeLog:
    
            * c-typeck.cc (build_c_cast): Exclude call to .ACCESS_WITH_SIZE from
            -Wbad-function-cast warnings.
    
    gcc/testsuite/ChangeLog:
    
            * gcc.dg/pointer-counted-by-pr123500.c: New test.

Diff:
---
 gcc/c/c-typeck.cc                                  |  3 ++-
 gcc/testsuite/gcc.dg/pointer-counted-by-pr123500.c | 13 +++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/gcc/c/c-typeck.cc b/gcc/c/c-typeck.cc
index 60ed44c2f672..098a4b553399 100644
--- a/gcc/c/c-typeck.cc
+++ b/gcc/c/c-typeck.cc
@@ -7455,7 +7455,8 @@ build_c_cast (location_t loc, tree type, tree expr)
 	warning_at (loc, OPT_Wpointer_to_int_cast,
 		    "cast from pointer to integer of different size");
 
-      if (TREE_CODE (value) == CALL_EXPR
+      if ((TREE_CODE (value) == CALL_EXPR
+	   && !is_access_with_size_p (value))
 	  && TREE_CODE (type) != TREE_CODE (otype))
 	warning_at (loc, OPT_Wbad_function_cast,
 		    "cast from function call of type %qT "
diff --git a/gcc/testsuite/gcc.dg/pointer-counted-by-pr123500.c b/gcc/testsuite/gcc.dg/pointer-counted-by-pr123500.c
new file mode 100644
index 000000000000..6f57ae5dd660
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pointer-counted-by-pr123500.c
@@ -0,0 +1,13 @@
+/* PR c/123500 */
+/* { dg-do compile } */
+/* { dg-options "-Wbad-function-cast" } */
+
+#include <stdint.h>
+struct buffer {
+  uint8_t * ptr __attribute__((counted_by(len)));
+  int len;
+};
+
+uintptr_t foo(struct buffer * b) {
+  return (uintptr_t)b->ptr;
+}