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From: Jeff Law <law@redhat.com>
To: Aldy Hernandez <aldyh@redhat.com>,
	       Richard Biener <richard.guenther@gmail.com>
Cc: gcc-patches <gcc-patches@gcc.gnu.org>, Pedro Alves <palves@redhat.com>
Subject: Re: protected alloca class for malloc fallback
Date: Fri, 05 Aug 2016 16:23:00 -0000	[thread overview]
Message-ID: <082fc386-345c-efa1-e1cd-053b1aa989a3@redhat.com> (raw)
In-Reply-To: <57A4A4B9.9090908@redhat.com>

On 08/05/2016 08:37 AM, Aldy Hernandez wrote:
>
> After looking at all this code, I realize no size will fit all if we
> want something clean.  So, I take my approach back.  I think we're best
> served by a couple different approaches, depending on usage.
Yup.

>
> My question is, how wed are we to an alloca based approach?  Can we
> replace the non-critical uses by std::string (diagnostics,
> BLAH_check_failed(), building a string to manipulate the output of
> env("SOME_VAR"), etc?).
I don't think we are at all wed to alloca.

>
> Then for things like the GCC driver wanting to create a vector of passed
> commands, we could use auto_vec<> (*gasp*, using a vector to represent a
> vector ;-)).  Note that auto_vec<> uses malloc (or GC) but creating a
> malloc'd vector at startup is hardly on the fast path.
>
> For the remaining things we could use either alloca with a malloc
> fallback for trivial things like set_user_assembler_name() that only
> have one exit point, or take it on a case by case basis.
>
> But it seems to me that we can use an STL container for the non critical
> things (which are the majority of them), and something else (perhaps an
> RAII thinggie TBD later).
>
> Is this reasonable?  I'd like to know before I spend any time converting
> anything to std::string and auto_vec<>.
Yes, this is all reasonable to me.  I'm a big believer in moving towards 
standard library implementations of things.  In this case we get to 
remove the allocas *and* make the code easier to grok for those that are 
familiar with the C++ standard library.

Jeff

  parent reply	other threads:[~2016-08-05 16:23 UTC|newest]

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-08-04 11:30 Aldy Hernandez
2016-08-04 12:58 ` Richard Biener
2016-08-04 15:19   ` Aldy Hernandez
2016-08-04 19:24     ` Jeff Law
2016-08-05 14:37       ` Aldy Hernandez
2016-08-05 15:15         ` Pedro Alves
2016-08-05 16:23         ` Jeff Law [this message]
2016-08-05 17:48           ` Richard Biener
2016-08-05  8:17     ` Richard Biener
2016-08-04 19:06 ` Pedro Alves
2016-08-04 19:16   ` Jeff Law
2016-08-04 19:22     ` Pedro Alves
2016-08-04 19:26       ` Jeff Law
2016-08-04 19:31         ` Pedro Alves
2016-08-05  2:10 ` Martin Sebor
2016-08-05 14:42   ` Aldy Hernandez
2016-08-05 17:56     ` Richard Biener
2016-08-05 18:16       ` Oleg Endo
2016-08-05 20:07         ` Richard Biener
2016-08-06 10:09           ` Aldy Hernandez
2016-08-06 10:15           ` Aldy Hernandez
2016-08-06 15:08             ` Richard Biener
2016-08-08 17:00               ` Jeff Law
2016-08-08 17:32                 ` Trevor Saunders
2016-08-08 19:03                   ` Richard Biener
2016-08-09 11:34                   ` Oleg Endo
2016-08-09 17:34                     ` Trevor Saunders
2016-08-10 17:03                       ` Oleg Endo
2016-08-11  1:23                         ` Trevor Saunders
2016-08-11 12:18                           ` Oleg Endo
2016-08-11 17:55                             ` Trevor Saunders
2016-08-20  2:29                         ` Mike Stump
2016-08-21 20:00                           ` C++11? (Re: protected alloca class for malloc fallback) Pedro Alves
2016-08-22  7:10                             ` Trevor Saunders
2016-08-22  7:28                               ` Richard Biener
2016-08-22 12:02                             ` Eric Gallager
2016-08-22 12:58                               ` Manuel López-Ibáñez
2016-08-22 22:08                               ` Mike Stump
2016-08-23 23:17                                 ` Eric Gallager
2016-08-09 13:17       ` protected alloca class for malloc fallback Aldy Hernandez
2016-08-09 13:21         ` Bernd Schmidt
2016-08-10 10:04         ` Richard Biener
2016-08-10 10:12           ` Aldy Hernandez
2016-08-10 10:39             ` Richard Biener
2016-08-10 18:00           ` Jeff Law
2016-08-10 18:33             ` Richard Biener
2016-08-16 16:28               ` Jeff Law
2016-08-16 16:44                 ` Jakub Jelinek
2016-08-16 16:47                   ` Jeff Law
2016-08-16 17:54                     ` Martin Sebor
2016-08-17  8:27                       ` Richard Biener
2016-08-17 13:39                         ` Martin Sebor

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