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From: archie@dellroad.org To: gcc-gnats@gcc.gnu.org Subject: c/10231: Request a "reachable" attribute for labels. Date: Wed, 26 Mar 2003 21:56:00 -0000 [thread overview] Message-ID: <20030326214607.5701.qmail@sources.redhat.com> (raw) >Number: 10231 >Category: c >Synopsis: Request a "reachable" attribute for labels. >Confidential: no >Severity: serious >Priority: medium >Responsible: unassigned >State: open >Class: change-request >Submitter-Id: net >Arrival-Date: Wed Mar 26 21:56:00 UTC 2003 >Closed-Date: >Last-Modified: >Originator: "Archie Cobbs" <archie@dellroad.org> >Release: 2.95.4 >Organization: >Environment: FreeBSD 4.8 >Description: Consider this code: foo() { goto lable3; label2: printf("don't eliminate me\n"); label3: printf("ok I'm here now\n"); } When optimizing -O2 GCC will eliminate the code between label2 and label3. However I have an application where I need this code to remain, because I've made the address of label2 available (via "&&label2") and also have some asm() statements that are used to jump to label2 that GCC doesn't know about. The only way to force GCC to keep the code is to do add reachable code that does something like this: if (non-constant expression that's never true) goto label2; This is a wasteful and ugly kludge though. It would be nicer if you could simply add a "reachable" attribute to a label that would tell GCC the label is reachable even if GCC thinks otherwise. So the example would become: foo() { goto lable3; label2 __attribute__ ((reachable)): printf("don't eliminate me\n"); label3: printf("ok I'm here now\n"); } >How-To-Repeat: >Fix: >Release-Note: >Audit-Trail: >Unformatted:
next reply other threads:[~2003-03-26 21:56 UTC|newest] Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top 2003-03-26 21:56 archie [this message] 2003-03-26 22:16 Zack Weinberg 2003-03-26 23:16 Archie Cobbs 2003-03-27 0:59 geoffk
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