[gcc r13-7246] c: Avoid -Wenum-int-mismatch warning for redeclaration of builtin acc_on_device [PR107041]

[gcc r13-7246] c: Avoid -Wenum-int-mismatch warning for redeclaration of builtin acc_on_device [PR107041]

[Jakub Jelinek]

https://gcc.gnu.org/g:f8646b8dcb18721e776c39117f62aee7ee571f21

commit r13-7246-gf8646b8dcb18721e776c39117f62aee7ee571f21
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Thu Apr 20 19:26:17 2023 +0200

    c: Avoid -Wenum-int-mismatch warning for redeclaration of builtin acc_on_device [PR107041]
    
    The new -Wenum-int-mismatch warning triggers with -Wsystem-headers in
    <openacc.h>, for obvious reasons the builtin acc_on_device uses int
    type argument rather than enum which isn't defined yet when the builtin
    is created, while the OpenACC spec requires it to have acc_device_t
    enum argument.  The header makes sure it has int underlying type by using
    negative and __INT_MAX__ enumerators.
    
    I've tried to make the builtin typegeneric or just varargs, but that
    changes behavior e.g. when one calls it with some C++ class which has
    cast operator to acc_device_t, so the following patch instead disables
    the warning for this builtin.
    
    2023-04-20  Jakub Jelinek  <jakub@redhat.com>
    
            PR c/107041
            * c-decl.cc (diagnose_mismatched_decls): Avoid -Wenum-int-mismatch
            warning on acc_on_device declaration.
    
            * gcc.dg/goacc/pr107041.c: New test.
    
    (cherry picked from commit 3d7ab53d6c59499624aa41c8dea0664976820b3b)

Diff:
---
 gcc/c/c-decl.cc                       |  9 ++++++++-
 gcc/testsuite/gcc.dg/goacc/pr107041.c | 23 +++++++++++++++++++++++
 2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/gcc/c/c-decl.cc b/gcc/c/c-decl.cc
index e537d33f398..1b53f2d0785 100644
--- a/gcc/c/c-decl.cc
+++ b/gcc/c/c-decl.cc
@@ -2219,7 +2219,14 @@ diagnose_mismatched_decls (tree newdecl, tree olddecl,
     }
   /* Warn about enum/integer type mismatches.  They are compatible types
      (C2X 6.7.2.2/5), but may pose portability problems.  */
-  else if (enum_and_int_p && TREE_CODE (newdecl) != TYPE_DECL)
+  else if (enum_and_int_p
+	   && TREE_CODE (newdecl) != TYPE_DECL
+	   /* Don't warn about about acc_on_device built-in redeclaration,
+	      the built-in is declared with int rather than enum because
+	      the enum isn't intrinsic.  */
+	   && !(TREE_CODE (olddecl) == FUNCTION_DECL
+		&& fndecl_built_in_p (olddecl, BUILT_IN_ACC_ON_DEVICE)
+		&& !C_DECL_DECLARED_BUILTIN (olddecl)))
     warned = warning_at (DECL_SOURCE_LOCATION (newdecl),
 			 OPT_Wenum_int_mismatch,
 			 "conflicting types for %q+D due to enum/integer "
diff --git a/gcc/testsuite/gcc.dg/goacc/pr107041.c b/gcc/testsuite/gcc.dg/goacc/pr107041.c
new file mode 100644
index 00000000000..ed7fb5a5b5d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/goacc/pr107041.c
@@ -0,0 +1,23 @@
+/* PR c/107041 */
+/* { dg-do compile } */
+/* { dg-additional-options "-Wenum-int-mismatch" } */
+
+typedef enum acc_device_t {
+  acc_device_current = -1,
+  acc_device_none = 0,
+  acc_device_default = 1,
+  acc_device_host = 2,
+  acc_device_not_host = 4,
+  acc_device_nvidia = 5,
+  acc_device_radeon = 8,
+  _ACC_highest = __INT_MAX__
+} acc_device_t;
+
+int acc_on_device (acc_device_t);		/* { dg-bogus "conflicting types for 'acc_on_device' due to enum/integer mismatch; have 'int\\\(acc_device_t\\\)'" } */
+int acc_on_device (acc_device_t);
+
+int
+foo (void)
+{
+  return acc_on_device (acc_device_host);
+}