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Re: [PATCH] middle-end/23155 ICE with union cast and array subscriptting
- From: Ian Lance Taylor <ian at airs dot com>
- To: Andrew Pinski <pinskia at physics dot uc dot edu>
- Cc: gcc-patches at gcc dot gnu dot org
- Date: 03 Nov 2005 00:02:21 -0800
- Subject: Re: [PATCH] middle-end/23155 ICE with union cast and array subscriptting
- References: <200510280335.j9S3Z2P3025937@earth.phy.uc.edu>
Andrew Pinski <pinskia@physics.uc.edu> writes:
> ChangeLog:
> * gimplifier.c (gimplify_expr): Create a temporary for lvalue
> CONSTRUCTOR.
>
> testsuite/ChangeLog:
>
> * gcc.dg/union-cast-1.c: New test.
> * gcc.dg/union-cast-2.c: New test.
> * gcc.dg/union-cast-3.c: New test.
This is OK, except for this comment:
+ /* A GNU extension that allows a cast to an union and C99 allows
+ non lvalue arrays to be subscriptted which cause this issue.
+ This has undefined behavior only on
+ execution, so create a temporary if an lvalue is
+ required. */
How about something along the lines of:
/* C99 code may assign to an array in a constructed
structure or union, and this has undefined behavior only
on execution, so create a temporary if an lvalue is
required. */
The intention is to be parallel to the existing comments for the
similar cases.
In particular, I don't think this has anything to do with unions. I
can recreate the ICE with this C++ test case (the test case works in C
because constructed structures are handled differently by the C
frontend).
struct s { int a[1]; };
void
foo5 (void)
{
((struct s) { { 0 } }).a[0] = 1;
}
Please do confirm that your patch fixes this C++ test case as well.
Thanks.
Ian