extern void v;
void f(void) { &v; }
is invalid in both C90 and C99: lvalues cannot have type void, although they can
have types const void or volatile void, and none of the other possibilities for
operands on '&' are met. However, GCC fails to diagnose this code.
extern void *p;
void f(void) { &*p; }
is invalid in C90 (for the same reason) but valid in C99 because the result of a
'*' operator is a permitted operand for '&' in C99 even if not an lvalue. GCC
gives a warning "dereferencing 'void *' pointer", but not an error with
-pedantic-errors. In C90 mode, but not in C99 mode, the use of '&' in this code
should receive a pedwarn. See also DRs 012 and 106.
I hope to fix these issues properly for 4.2 by moving information about whether
an expression has the right syntax to be an lvalue, or is the result of * or []
operators, into the c_expr structure; the difference between the above cases is
why this naturally involves two flags rather than one in that structure. It is
however likely a simpler local fix could be found before then that examines the
trees to distinguish the two cases.
--
Summary: constraints on '&' not fully implemented
Product: gcc
Version: 4.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: jsm28 at gcc dot gnu dot org
CC: gcc-bugs at gcc dot gnu dot org
OtherBugsDependingO 16620,16989
nThis:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22367
