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* Re: c/10430: converting double word to quad word, cltd, cdq, 3.2.2
@ 2003-04-18 7:45 ebotcazou
0 siblings, 0 replies; 2+ messages in thread
From: ebotcazou @ 2003-04-18 7:45 UTC (permalink / raw)
To: aaron, gcc-bugs, gcc-prs, nobody
Synopsis: converting double word to quad word, cltd, cdq, 3.2.2
State-Changed-From-To: open->closed
State-Changed-By: ebotcazou
State-Changed-When: Fri Apr 18 07:45:23 2003
State-Changed-Why:
Not a bug. The code is equivalent to
extern int bar(void);
main()
{
foo((unsigned long long int) bar());
}
Since the return type of bar() is signed, the return value
must be sign-extended according to the ISO C standard, hence
the use of 'cltd'.
http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=10430
^ permalink raw reply [flat|nested] 2+ messages in thread
* c/10430: converting double word to quad word, cltd, cdq, 3.2.2
@ 2003-04-18 0:06 aaron
0 siblings, 0 replies; 2+ messages in thread
From: aaron @ 2003-04-18 0:06 UTC (permalink / raw)
To: gcc-gnats
>Number: 10430
>Category: c
>Synopsis: converting double word to quad word, cltd, cdq, 3.2.2
>Confidential: no
>Severity: serious
>Priority: medium
>Responsible: unassigned
>State: open
>Class: sw-bug
>Submitter-Id: net
>Arrival-Date: Fri Apr 18 00:06:00 UTC 2003
>Closed-Date:
>Last-Modified:
>Originator: Aaron Wegner
>Release: unknown-1.0
>Organization:
>Environment:
i686-pc-linux-gnu
>Description:
-------
Problem
-------
The problem is that cldt will replace whatever is in %edx with zeros or ones. Correct code omits cldt.
--------
C Source
--------
main()
{
foo((unsigned long long int) bar());
}
-------------------------
Generated Assember Source
-------------------------
.file "test.c"
.text
.globl main
.type main,@function
main:
pushl %ebp
movl %esp, %ebp
subl $8, %esp
andl $-16, %esp
movl $0, %eax
subl %eax, %esp
call bar
cltd
movl %eax, (%esp)
movl %edx, 4(%esp)
call foo
leave
ret
.Lfe1:
.size main,.Lfe1-main
.ident "GCC: (GNU) 3.2.2"
>How-To-Repeat:
gcc -S test.c
>Fix:
Unsure still.
>Release-Note:
>Audit-Trail:
>Unformatted:
^ permalink raw reply [flat|nested] 2+ messages in thread
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2003-04-18 7:45 c/10430: converting double word to quad word, cltd, cdq, 3.2.2 ebotcazou
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2003-04-18 0:06 aaron
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