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From: Suanhsi Yong <suan@cs.wisc.edu> To: gcc-gnats@gcc.gnu.org Subject: c/6409: C comma operator: wrong behavior Date: Mon, 22 Apr 2002 10:06:00 -0000 [thread overview] Message-ID: <200204221704.MAA00865@cygnet.cs.wisc.edu> (raw) >Number: 6409 >Category: c >Synopsis: C comma operator: wrong behavior >Confidential: no >Severity: serious >Priority: medium >Responsible: unassigned >State: open >Class: wrong-code >Submitter-Id: net >Arrival-Date: Mon Apr 22 10:06:01 PDT 2002 >Closed-Date: >Last-Modified: >Originator: Suanhsi Yong >Release: 3.0.3 >Organization: >Environment: System: Linux cygnet.cs.wisc.edu 2.4.17-csl1smp #1 SMP Mon Jan 7 16:44:21 CST 2002 i686 unknown Architecture: i686 host: i686-pc-linux-gnu build: i686-pc-linux-gnu target: i686-pc-linux-gnu configured with: /s/gcc-3.0.3/src/gcc-3.0.3/configure --prefix=/s/gcc-3.0.3/i386_rh72 --enable-shared --enable-threads Note: bug also manifested in <sparc-sun-solaris2.8> version, and version 3.0.4 (linux) as well. >Description: Best illustrated by example: 1. int val; 2. (val=11) 3. + (val=22, 4. printf("VAL = %d\n", val) 5. ); Line 4 outputs "11" rather than the expected "22". C specs define a sequence point at the comma operator, so by the "at-most-one-write" semantics of expressions, val should be 22 at line 4. (Its value at line 6, of course, is undefined, due to the arbitrary order-of-evaluation for the + operator.) >How-To-Repeat: Just compile (gcc, no special flags needed) and run the following: int main() { int val; (val=11) + (val=22, printf("VAL = %d\n", val)); return 0; } >Fix: Don't know. >Release-Note: >Audit-Trail: >Unformatted:
next reply other threads:[~2002-04-22 17:06 UTC|newest] Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top 2002-04-22 10:06 Suanhsi Yong [this message] 2002-04-22 10:16 jsm28
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