http://d.puremagic.com/issues/show_bug.cgi?id=6206
Summary: Pure function not called in comma expression in for
loop increment
Product: D
Version: D2
Platform: Other
OS/Version: Linux
Status: NEW
Keywords: wrong-code
Severity: normal
Priority: P2
Component: DMD
AssignedTo: [email protected]
ReportedBy: [email protected]
--- Comment #0 from Lars T. Kyllingstad <[email protected]> 2011-06-24
02:21:32 PDT ---
Test case:
struct S
{
int i = 0;
void incr() pure { ++i; }
}
void main()
{
S s;
for (int j=0; j<10; s.incr(), ++j) { }
assert (s.i == 10); // fails
}
The assert should pass, but it fails iff S.incr() is marked as pure. (In fact,
S.i is never increased at all in this case.) Note that moving '++j' into the
loop body makes the bug disappear. It seems the call to s.incr() must be part
of a comma expression for the bug to manifest.
While seemingly obscure, this has some very real consequences. For example, it
means std.algorithm.equal() doesn't work with ranges that have a pure
popFront().
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