[Bug c/60809] C99 struct initialiser with embedded self assignment
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60809 Marek Polacek changed: What|Removed |Added Status|UNCONFIRMED |SUSPENDED Last reconfirmed||2014-04-30 Ever confirmed|0 |1 --- Comment #7 from Marek Polacek --- (In reply to jos...@codesourcery.com from comment #6) > I see nothing that says anything about the sequencing of side effects in > initialization expressions with respect to the actual initialization > itself, or parts thereof - either to require a particular sequencing, or > to make it indeterminately sequenced or unsequenced. That may mean it's > implicitly unsequenced, but I'd suggest raising this with WG14. Thanks, I'll try to report it then; suspending for now.
[Bug c/60809] C99 struct initialiser with embedded self assignment
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60809 --- Comment #6 from joseph at codesourcery dot com --- I see nothing that says anything about the sequencing of side effects in initialization expressions with respect to the actual initialization itself, or parts thereof - either to require a particular sequencing, or to make it indeterminately sequenced or unsequenced. That may mean it's implicitly unsequenced, but I'd suggest raising this with WG14.
[Bug c/60809] C99 struct initialiser with embedded self assignment
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60809
--- Comment #5 from jimis ---
Andreas: On a second thought, this paragraph only talks about the order
*within* the initialisation list. But no matter of that order, the
initialisation list is always evaluated to:
{
.ai_family = AF_UNSPEC,
.ai_socktype = SOCK_STREAM,
AI_PASSIVE
};
The outer assignment to query2, should never set ai_flags, no matter what the
side-effects of the inner assignments are. Am I thinking right?
[Bug c/60809] C99 struct initialiser with embedded self assignment
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60809 --- Comment #4 from jimis --- Thanks Andreas, that's the reference I was looking for! I guess since this code triggers unspecified behaviour, a warning would be even more needed. :-)
[Bug c/60809] C99 struct initialiser with embedded self assignment
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60809 --- Comment #3 from Andreas Schwab --- 6.7.9 Initialization 23 The evaluations of the initialization list expressions are indeterminately sequenced with respect to one another and thus the order in which any side effects occur is unspecified.
[Bug c/60809] C99 struct initialiser with embedded self assignment
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60809
--- Comment #2 from jimis ---
(In reply to Marek Polacek from comment #1)
> I see nothing surprising here; an assignment expression has the value of the
> left operand after the assignment. So we 1) set query2.ai_flags to
> AI_PASSIVE, 2) use this value to initialize .ai_protocol.
if the outer assignment runs last, shouldn't it overwrite the inner assignment?
Then it should be equivalent to that:
struct addrinfo query3 = {
.ai_family = AF_UNSPEC,
.ai_socktype = SOCK_STREAM,
1
Which means that ai_flags should be 0.
[Bug c/60809] C99 struct initialiser with embedded self assignment
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60809 Marek Polacek changed: What|Removed |Added CC||mpolacek at gcc dot gnu.org --- Comment #1 from Marek Polacek --- I see nothing surprising here; an assignment expression has the value of the left operand after the assignment. So we 1) set query2.ai_flags to AI_PASSIVE, 2) use this value to initialize .ai_protocol. I'm not sure a warning here makes sense: an assignment-expression is perfectly valid initializer.
