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re PR c++/39480 (generated memcpy causes trouble in assignment) 

PR c++/39480
        * call.c (build_over_call): Don't call memcpy if the target is
        the same as the source.

From-SVN: r146013
This commit is contained in:
Jason Merrill 2009-04-13 16:56:45 -04:00 committed by Jason Merrill
parent 91ddafab4b
commit b68e185cc8
4 changed files with 56 additions and 1 deletions
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4
gcc/cp/ChangeLog
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@ -1,5 +1,9 @@
2009-04-13 Jason Merrill <jason@redhat.com>
PR c++/39480
* call.c (build_over_call): Don't call memcpy if the target is
the same as the source.
PR c++/39750
* pt.c (uses_template_parms): Handle CONSTRUCTOR.

18
gcc/cp/call.c
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@ -5391,17 +5391,33 @@ build_over_call (struct z_candidate *cand, int flags, tsubst_flags_t complain)
else
{
/* We must only copy the non-tail padding parts.
Use __builtin_memcpy for the bitwise copy. */
Use __builtin_memcpy for the bitwise copy.
FIXME fix 22488 so we can go back to using MODIFY_EXPR
instead of an explicit call to memcpy. */
tree arg0, arg1, arg2, t;
tree test = NULL_TREE;
arg2 = TYPE_SIZE_UNIT (as_base);
arg1 = arg;
arg0 = cp_build_unary_op (ADDR_EXPR, to, 0, complain);
if (!(optimize && flag_tree_ter))
{
/* When TER is off get_pointer_alignment returns 0, so a call
to __builtin_memcpy is expanded as a call to memcpy, which
is invalid with identical args. When TER is on it is
expanded as a block move, which should be safe. */
arg0 = save_expr (arg0);
arg1 = save_expr (arg1);
test = build2 (EQ_EXPR, boolean_type_node, arg0, arg1);
}
t = implicit_built_in_decls[BUILT_IN_MEMCPY];
t = build_call_n (t, 3, arg0, arg1, arg2);
t = convert (TREE_TYPE (arg0), t);
if (test)
t = build3 (COND_EXPR, TREE_TYPE (t), test, arg0, t);
val = cp_build_indirect_ref (t, 0, complain);
}

3
gcc/testsuite/ChangeLog
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@ -1,5 +1,8 @@
2009-04-13 Jason Merrill <jason@redhat.com>
PR c++/39480
* g++.dg/init/copy7.C: New.
PR c++/39750
* g++.dg/template/crash90.C: New.

32
gcc/testsuite/g++.dg/init/copy7.C Normal file
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@ -0,0 +1,32 @@
// PR c++/39480
// It isn't always safe to call memcpy with identical arguments.
// { dg-do run }
extern "C" void abort();
extern "C" void *
memcpy(void *dest, void *src, __SIZE_TYPE__ n)
{
abort();
}
struct A
{
double d[10];
};
struct B: public A
{
char bc;
};
B b;
void f(B *a1, B* a2)
{
*a1 = *a2;
}
int main()
{
f(&b,&b);
}