* [committed] c: Ignore _Atomic on function return type for C2x
@ 2023-05-15 23:18 Joseph Myers
0 siblings, 0 replies; only message in thread
From: Joseph Myers @ 2023-05-15 23:18 UTC (permalink / raw)
To: gcc-patches
For C2x it was decided that _Atomic would be completely ignored on
function return types (just as was done for qualifiers in C11 DR#423),
to eliminate the potential for an rvalue returned by a function having
_Atomic-qualified type when an rvalue resulting from lvalue-to-rvalue
conversion could not have such a type. Implement this for GCC.
Bootstrapped with no regressions for x86_64-pc-linux-gnu.
gcc/c/
* c-decl.cc (grokdeclarator): Ignore _Atomic on function return
type for C2x.
gcc/testsuite/
* gcc.dg/qual-return-9.c, gcc.dg/qual-return-10.c: New tests.
diff --git a/gcc/c/c-decl.cc b/gcc/c/c-decl.cc
index 1b53f2d0785..90d7cd27cd5 100644
--- a/gcc/c/c-decl.cc
+++ b/gcc/c/c-decl.cc
@@ -7412,9 +7412,12 @@ grokdeclarator (const struct c_declarator *declarator,
them for noreturn functions. The resolution of C11
DR#423 means qualifiers (other than _Atomic) are
actually removed from the return type when
- determining the function type. */
+ determining the function type. For C2X, _Atomic is
+ removed as well. */
int quals_used = type_quals;
- if (flag_isoc11)
+ if (flag_isoc2x)
+ quals_used = 0;
+ else if (flag_isoc11)
quals_used &= TYPE_QUAL_ATOMIC;
if (quals_used && VOID_TYPE_P (type) && really_funcdef)
pedwarn (specs_loc, 0,
diff --git a/gcc/testsuite/gcc.dg/qual-return-10.c b/gcc/testsuite/gcc.dg/qual-return-10.c
new file mode 100644
index 00000000000..c7dd6adc4c6
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/qual-return-10.c
@@ -0,0 +1,12 @@
+/* Test qualifiers on function return types in C2X (C2X version of
+ qual-return-6.c): those qualifiers are now ignored for all purposes,
+ including _Atomic, but should still get warnings. */
+/* { dg-do compile } */
+/* { dg-options "-std=c2x -Wignored-qualifiers" } */
+
+const int f1 (void); /* { dg-warning "qualifiers ignored" } */
+volatile int f2 (void) { return 0; } /* { dg-warning "qualifiers ignored" } */
+const volatile void f3 (void) { } /* { dg-warning "qualifiers ignored" } */
+const void f4 (void); /* { dg-warning "qualifiers ignored" } */
+_Atomic int f5 (void); /* { dg-warning "qualifiers ignored" } */
+_Atomic int f6 (void) { return 0; } /* { dg-warning "qualifiers ignored" } */
diff --git a/gcc/testsuite/gcc.dg/qual-return-9.c b/gcc/testsuite/gcc.dg/qual-return-9.c
new file mode 100644
index 00000000000..7762782edf0
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/qual-return-9.c
@@ -0,0 +1,32 @@
+/* Test qualifiers on function return types in C2X (C2X version of
+ qual-return-5.c): those qualifiers are now ignored for all purposes,
+ including _Atomic. */
+/* { dg-do compile } */
+/* { dg-options "-std=c2x -pedantic-errors" } */
+
+int f1 (void);
+const int f1 (void);
+volatile int f1 (void) { return 0; }
+
+int *restrict f2 (void) { return 0; }
+int *f2 (void);
+
+const volatile long f3 (void);
+long f3 (void);
+
+const volatile void f4 (void) { }
+void f4 (void);
+
+_Atomic int f5 (void);
+int f5 (void);
+
+int f6 (void);
+_Atomic int f6 (void) { return 0; }
+
+/* The standard seems unclear regarding the case where restrict is
+ applied to a function return type that may not be
+ restrict-qualified; assume here that it is disallowed. */
+restrict int f7 (void); /* { dg-error "restrict" } */
+
+typedef void FT (void);
+FT *restrict f8 (void); /* { dg-error "restrict" } */
--
Joseph S. Myers
joseph@codesourcery.com
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