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Constraints on unary '&' (PR 22367)
- From: "Joseph S. Myers" <joseph at codesourcery dot com>
- To: gcc-patches at gcc dot gnu dot org
- Date: Sat, 18 Apr 2009 22:34:52 +0000 (UTC)
- Subject: Constraints on unary '&' (PR 22367)
This patch fixes PR 22367, a bug where the C front end failed to check
the exact constraints on unary '&' operators (which differ between C90
and C99).
Bootstrapped with no regressions on x86_64-unknown-linux-gnu. Applied
to mainline.
2009-04-18 Joseph Myers <joseph@codesourcery.com>
PR c/22367
* c-typeck.c (build_unary_op): Check for taking address of
expression of type void.
testsuite:
2009-04-18 Joseph Myers <joseph@codesourcery.com>
PR c/22367
* gcc.dg/lvalue-6.c, gcc.dg/lvalue-7.c: New tests.
Index: gcc/c-typeck.c
===================================================================
--- gcc/c-typeck.c (revision 146291)
+++ gcc/c-typeck.c (working copy)
@@ -3335,6 +3335,15 @@ build_unary_op (location_t location,
case ADDR_EXPR:
/* Note that this operation never does default_conversion. */
+ /* The operand of unary '&' must be an lvalue (which excludes
+ expressions of type void), or, in C99, the result of a [] or
+ unary '*' operator. */
+ if (VOID_TYPE_P (TREE_TYPE (arg))
+ && TYPE_QUALS (TREE_TYPE (arg)) == TYPE_UNQUALIFIED
+ && (TREE_CODE (arg) != INDIRECT_REF
+ || !flag_isoc99))
+ pedwarn (location, 0, "taking address of expression of type %<void%>");
+
/* Let &* cancel out to simplify resulting code. */
if (TREE_CODE (arg) == INDIRECT_REF)
{
Index: gcc/testsuite/gcc.dg/lvalue-6.c
===================================================================
--- gcc/testsuite/gcc.dg/lvalue-6.c (revision 0)
+++ gcc/testsuite/gcc.dg/lvalue-6.c (revision 0)
@@ -0,0 +1,17 @@
+/* Test constraints on unary '&': PR 22367. */
+
+/* { dg-do compile } */
+/* { dg-options "-std=iso9899:1990 -pedantic-errors" } */
+
+extern void v;
+void f1 (void) { &v; } /* { dg-error "taking address of expression of type 'void'" } */
+
+extern void *pv;
+void f2 (void) { &*pv; } /* { dg-warning "dereferencing" } */
+/* { dg-error "taking address of expression of type 'void'" "C90 only error" { target *-*-* } 10 } */
+
+extern const void cv;
+void f3 (void) { &cv; }
+
+extern const void *pcv;
+void f4 (void) { &*pcv; } /* { dg-warning "dereferencing" } */
Index: gcc/testsuite/gcc.dg/lvalue-7.c
===================================================================
--- gcc/testsuite/gcc.dg/lvalue-7.c (revision 0)
+++ gcc/testsuite/gcc.dg/lvalue-7.c (revision 0)
@@ -0,0 +1,16 @@
+/* Test constraints on unary '&': PR 22367. */
+
+/* { dg-do compile } */
+/* { dg-options "-std=iso9899:1999 -pedantic-errors" } */
+
+extern void v;
+void f1 (void) { &v; } /* { dg-error "taking address of expression of type 'void'" } */
+
+extern void *pv;
+void f2 (void) { &*pv; } /* { dg-warning "dereferencing" } */
+
+extern const void cv;
+void f3 (void) { &cv; }
+
+extern const void *pcv;
+void f4 (void) { &*pcv; } /* { dg-warning "dereferencing" } */
--
Joseph S. Myers
joseph@codesourcery.com