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From: "gabravier at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/102939] New: Ridiculously long compilation times on (admittedly ridiculous) pointer declaration
Date: Mon, 25 Oct 2021 22:37:14 +0000	[thread overview]
Message-ID: <bug-102939-4@http.gcc.gnu.org/bugzilla/> (raw)

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102939

            Bug ID: 102939
           Summary: Ridiculously long compilation times on (admittedly
                    ridiculous) pointer declaration
           Product: gcc
           Version: 11.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gabravier at gmail dot com
  Target Milestone: ---

#define PTR1 * * * * * * * * * *
#define PTR2 PTR1 PTR1 PTR1 PTR1 PTR1 PTR1 PTR1 PTR1 PTR1 PTR1
#define PTR3 PTR2 PTR2 PTR2 PTR2 PTR2 PTR2 PTR2 PTR2 PTR2 PTR2
#define PTR4 PTR3 PTR3 PTR3 PTR3 PTR3 PTR3 PTR3 PTR3 PTR3 PTR3
#define PTR5 PTR4 PTR4 PTR4 PTR4 PTR4 PTR4 PTR4 PTR4 PTR4 PTR4
#define PTR6 PTR5 PTR5 PTR5 PTR5 PTR5 PTR5 PTR5 PTR5 PTR5 PTR5

int PTR4 q3_var = 0;

This takes an entire second to compile for GCC, and which is absolutely
ridiculous compared to, for example, tcc and ack, which both compile this code
in under .01 seconds.

I've investigated a bit into what's going on myself and it looks like while
parsing, there's some `variably_modified_type_p` algorithm that's going haywire
and taking forever on this declaration. Is it some kind of O(n²) recursive
algorithm or something ? It seems rather quite odd, to be honest...

For comparison, compiling this as C++ takes just .04 seconds.

             reply	other threads:[~2021-10-25 22:37 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-25 22:37 gabravier at gmail dot com [this message]
2021-10-25 22:50 ` [Bug c/102939] Ridiculously long compilation times on (admittedly itself " pinskia at gcc dot gnu.org
2021-10-26  7:16 ` rguenth at gcc dot gnu.org
2021-10-31 20:27 ` hp at gcc dot gnu.org
2021-11-01  8:41 ` gabravier at gmail dot com
2023-02-18 21:56 ` muecker at gwdg dot de
2023-12-17 19:49 ` uecker at gcc dot gnu.org

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