OpenE2K/gcc
2
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

Support C2x [[maybe_unused]] attribute.

Browse Source 
This patch adds support for the C2x [[maybe_unused]] attribute, using
the same handler as for GNU __attribute__ ((unused)).

As with other such attribute support, I think turning certain warnings
into pedwarns for usage in cases where that is a constraint violation
can be addressed later as a bug fix, as can the C2x constraint for
various standard attributes that they do not appear more than once
inside a single [[]].

However, the warnings that appear in c2x-attr-maybe_unused-1.c (that
the attribute is ignored on member declarations) need to remain as
warnings not pedwarns, since C2x does permit the attribute there.  (Or
they could be silenced, on the basis that GCC doesn't have warnings
for unused struct and union members so it's completely harmless that
it's ignoring an attribute that might do something useful with another
compiler that does have such warnings.)

Bootstrapped with no regressions on x86_64-pc-linux-gnu.

gcc/c:
	* c-decl.c (std_attribute_table): Add maybe_unused.

gcc/testsuite:
	* gcc.dg/c2x-attr-maybe_unused-1.c,
	gcc.dg/c2x-attr-maybe_unused-2.c,
	gcc.dg/c2x-attr-maybe_unused-3.c: New tests.

From-SVN: r278310
This commit is contained in:
Joseph Myers 2019-11-15 18:39:35 +00:00 committed by Joseph Myers
parent a91eb2341f
commit 97cc11871e
6 changed files with 79 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
gcc/c/ChangeLog
View File

@ -1,3 +1,7 @@
2019-11-15 Joseph Myers <joseph@codesourcery.com>
* c-decl.c (std_attribute_table): Add maybe_unused.
2019-11-15 Joseph Myers <joseph@codesourcery.com>
* c-decl.c (std_attribute_table): Add fallthrough.

2
gcc/c/c-decl.c
View File

@ -4345,6 +4345,8 @@ const struct attribute_spec std_attribute_table[] =
handle_deprecated_attribute, NULL },
{ "fallthrough", 0, 0, false, false, false, false,
handle_fallthrough_attribute, NULL },
{ "maybe_unused", 0, 0, false, false, false, false,
handle_unused_attribute, NULL },
{ NULL, 0, 0, false, false, false, false, NULL, NULL }
};

6
gcc/testsuite/ChangeLog
View File

@ -1,3 +1,9 @@
2019-11-15 Joseph Myers <joseph@codesourcery.com>
* gcc.dg/c2x-attr-maybe_unused-1.c,
gcc.dg/c2x-attr-maybe_unused-2.c,
gcc.dg/c2x-attr-maybe_unused-3.c: New tests.
2019-11-15 Matthew Malcomson <matthew.malcomson@arm.com>
* gcc.dg/rtl/aarch64/rtl-handle-column-numbers.c: New test.

31
gcc/testsuite/gcc.dg/c2x-attr-maybe_unused-1.c Normal file
View File

@ -0,0 +1,31 @@
/* Test C2x maybe_unused attribute: valid uses. */
/* { dg-do compile } */
/* { dg-options "-std=c2x -pedantic-errors -Wall -Wextra -Wunused" } */
[[maybe_unused]] static void f1 (void) {}
[[__maybe_unused__]] const int c1 = 1;
static int c2 [[maybe_unused]] = 2;
int
g ([[maybe_unused]] int x, int y)
{
[[maybe_unused]] typedef float F;
[[maybe_unused]] int a;
int b [[__maybe_unused__]];
int c [[maybe_unused]];
c = y;
return y;
}
struct [[maybe_unused]] s { double d; };
struct s2 { [[__maybe_unused__]] int a; int b [[maybe_unused]]; } x; /* { dg-warning "attribute ignored" } */
enum e { E1 [[maybe_unused]] };
union [[maybe_unused]] u { int x; };
enum [[maybe_unused]] eu { E2 };
union u2 { [[maybe_unused]] int a; int b [[maybe_unused]]; } y; /* { dg-warning "attribute ignored" } */

25
gcc/testsuite/gcc.dg/c2x-attr-maybe_unused-2.c Normal file
View File

@ -0,0 +1,25 @@
/* Test C2x maybe_unused attribute: invalid contexts. */
/* { dg-do compile } */
/* { dg-options "-std=c2x -pedantic-errors" } */
/* This attribute is not valid in most cases on types other than their
definitions, or on statements, or as an attribute-declaration. */
[[maybe_unused]]; /* { dg-warning "ignored" } */
int [[maybe_unused]] var; /* { dg-warning "ignored" } */
/* { dg-message "that appertains to a type-specifier" "appertains" { target *-*-* } .-1 } */
int array_with_dep_type[2] [[maybe_unused]]; /* { dg-warning "ignored" } */
/* { dg-message "that appertains to a type-specifier" "appertains" { target *-*-* } .-1 } */
void fn_with_dep_type () [[maybe_unused]]; /* { dg-warning "ignored" } */
/* { dg-message "that appertains to a type-specifier" "appertains" { target *-*-* } .-1 } */
void
f (void)
{
int a;
[[maybe_unused]]; /* { dg-warning "ignored" } */
[[maybe_unused]] a = 1; /* { dg-warning "ignored" } */
}

11
gcc/testsuite/gcc.dg/c2x-attr-maybe_unused-3.c Normal file
View File

@ -0,0 +1,11 @@
/* Test C2x maybe_unused attribute: invalid syntax. */
/* { dg-do compile } */
/* { dg-options "-std=c2x -pedantic-errors" } */
[[maybe_unused()]] int a; /* { dg-error "does not take any arguments" } */
[[maybe_unused(0)]] int b; /* { dg-error "does not take any arguments|expected" } */
[[maybe_unused("", 123)]] int c; /* { dg-error "does not take any arguments|expected" } */
[[maybe_unused("")]] int d; /* { dg-error "does not take any arguments|expected" } */