digitalmars.D.bugs - [Issue 2682] New: const struct initialized with struct literal recreates value on stack when used
- d-bugmail puremagic.com (34/34) Feb 22 2009 http://d.puremagic.com/issues/show_bug.cgi?id=2682
- d-bugmail puremagic.com (8/8) Feb 22 2009 http://d.puremagic.com/issues/show_bug.cgi?id=2682
- d-bugmail puremagic.com (16/16) Mar 02 2009 http://d.puremagic.com/issues/show_bug.cgi?id=2682
- d-bugmail puremagic.com (6/6) Mar 29 2009 http://d.puremagic.com/issues/show_bug.cgi?id=2682
http://d.puremagic.com/issues/show_bug.cgi?id=2682
Summary: const struct initialized with struct literal recreates
value on stack when used
Product: D
Version: 1.039
Platform: PC
OS/Version: Linux
Status: NEW
Keywords: wrong-code
Severity: normal
Priority: P2
Component: DMD
AssignedTo: bugzilla digitalmars.com
ReportedBy: kamm-removethis incasoftware.de
As the following code shows the const S s isn't really initialized with a
constant that's put into the data segment, but works more like "alias S(5) s;".
---
struct S { int i; }
const S s = S(5);
const S u = { 5 };
void foo(int num) {
printf("%p %p\n", &s, &u);
if (num > 0)
foo(num-1);
}
void main() {
foo(2);
}
---
output:
0xbfc1774c 0x80601a0
0xbfc17738 0x80601a0
0xbfc17724 0x80601a0
--
Feb 22 2009
d-bugmail puremagic.com
http://d.puremagic.com/issues/show_bug.cgi?id=2682
smjg iname.com changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |smjg iname.com
This reminds me of bug 2414 ... related?
--
Feb 22 2009
http://d.puremagic.com/issues/show_bug.cgi?id=2682
I fixed this in LDC by disabling the Initializer -> Expression optimization for
StructInitializerS:
--- a/dmd/optimize.c Tue Mar 03 02:51:21 2009 +0100
+++ b/dmd/optimize.c Tue Mar 03 04:38:49 2009 +0100
-46,7 +46,7
if (e1->op == TOKvar)
{ VarExp *ve = (VarExp *)e1;
VarDeclaration *v = ve->var->isVarDeclaration();
- if (v && v->isConst() && v->init)
+ if (v && v->isConst() && v->init && !v->init->isStructInitializer())
{ Expression *ei = v->init->toExpression();
if (ei && ei->type)
e1 = ei;
--
Mar 02 2009
http://d.puremagic.com/issues/show_bug.cgi?id=2682 ------- Removing that optimization lead to constant folding issues. Instead we have now demoted struct literals to rvalues in LDC. It does not create any regressions in our testsuite - please let us know if you expect this to be trouble. --
Mar 29 2009