[PATCH v2] c: Fix crash in c-typeck.cc convert_arguments with indirect calls

[Florian Weimer]

gcc/c/

        PR c/120055
        * c-typeck.cc (convert_arguments): Check if fundecl is null
        before checking for builtin function declaration.

gcc/testsuite/

        * gcc.dg/Wdeprecated-non-prototype-6.c: New test.

---
v2: Fix condition to keep diagnosing indirect calls.  Add a test case
    for that.

 gcc/c/c-typeck.cc                                  |  2 +-
 gcc/testsuite/gcc.dg/Wdeprecated-non-prototype-6.c | 14 ++++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/gcc/c/c-typeck.cc b/gcc/c/c-typeck.cc
index c7a13bf2b2f..05fb129ada8 100644
--- a/gcc/c/c-typeck.cc
+++ b/gcc/c/c-typeck.cc
@@ -4337,7 +4337,7 @@ convert_arguments (location_t loc, vec<location_t> 
arg_loc, tree fntype,
        }
 
       if (!typetail && parmnum == 0 && !TYPE_NO_NAMED_ARGS_STDARG_P (fntype)
-         && !fndecl_built_in_p (fundecl))
+         && !(fundecl && fndecl_built_in_p (fundecl)))
        {
          auto_diagnostic_group d;
          bool warned;
diff --git a/gcc/testsuite/gcc.dg/Wdeprecated-non-prototype-6.c 
b/gcc/testsuite/gcc.dg/Wdeprecated-non-prototype-6.c
new file mode 100644
index 00000000000..08f2995d5b2
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Wdeprecated-non-prototype-6.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-std=gnu17 -Wdeprecated-non-prototype" } */
+
+void (*f1) ();
+void (*f2) ();
+void (*f3) (...);
+
+void
+g ()
+{
+  f1 ();
+  f2 (1); /* { dg-warning "does not allow arguments for function" } */
+  f3 (1);
+}

base-commit: fd013e3fe47f2623b581213c6d7c08bdbd5b1614