On Tue, 26 Sep 2006, ext Thomas Graf wrote:
> You're right, 0x80000000 - 1 is already positive. Ignore the patch.
basic_change() won't work without this patch if we compile the
kernel with the GCC version in RHEL5...
gcc version 4.1.1 20060817 (Red Hat 4.1.1-18)
which optimizes the code like this (objdump -S inttest.c) ...
int main()
{
0: 55 push %ebp
1: 89 e5 mov %esp,%ebp
int i = 0x80000000;
do {
printf(KERN_ERR "in do %d\n", i);
3: 68 00 00 00 80 push $0x80000000
8: 68 00 00 00 00 push $0x0
d: e8 fc ff ff ff call e <main+0xe>
} while (--i > 0);
printf(KERN_ERR "out of do %d\n", i);
12: 68 00 00 00 80 push $0x80000000
17: 68 0a 00 00 00 push $0xa
1c: e8 fc ff ff ff call 1d <main+0x1d>
return 0;
}
21: 31 c0 xor %eax,%eax
23: c9 leave
24: c3 ret
# ./inttest
in do -2147483648
out of do -2147483648
gcc -m32 -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs
-fno-strict-aliasing -fno-common -Wstrict-prototypes -Wundef
-Werror-implicit-function-declaration -fno-stack-protector -Os
-fno-omit-frame-pointer -fno-optimize-sibling-calls
-fasynchronous-unwind-tables -g -pipe -msoft-float
-fno-builtin-sprintf -fno-builtin-log2 -fno-builtin-puts
-mpreferred-stack-boundary=2 -march=i686 -mtune=generic
-mtune=generic -mregparm=3 -ffreestanding
-Wdeclaration-after-statement -Wno-pointer-sign -c -o
inttest.o inttest.c
So I would suggest to apply this patch to be compatible with the
GCC version in RHEL5, and simply to make code clearer (to the
intended idea).
--KimN
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