Bug#412617: marked as done (gcc-4.1: -O2 optimises away necessary code with no warning)
Your message dated Tue, 27 Feb 2007 10:03:42 +0100
with message-id <[EMAIL PROTECTED]>
and subject line Bug#412617: gcc-4.1: -O2 optimises away necessary code with no
warning
has caused the attached Bug report to be marked as done.
This means that you claim that the problem has been dealt with.
If this is not the case it is now your responsibility to reopen the
Bug report if necessary, and/or fix the problem forthwith.
(NB: If you are a system administrator and have no idea what I am
talking about this indicates a serious mail system misconfiguration
somewhere. Please contact me immediately.)
Debian bug tracking system administrator
(administrator, Debian Bugs database)
--- Begin Message ---
Package: gcc-4.1
Version: 4.1.1-21
Severity: normal
The below code should return a random number between 0 and 1, but does
not do that when -O2 or higher is enabled. Uncomment the printf line
to make the code work properly.
Cheers,
//Anders
#include
#include
#include
#include
uint32_t rngi(uint32_t* ws)
{
/* Dummy code in place of more advanced RNG */
return rand() | ((rand() & 0x1)<<31);
}
static inline double rng(uint32_t* ws)
{
/* Create 53 bit random number */
uint64_t r = 0ULL;
void* rp = &r;
((uint32_t*)rp)[1] = rngi(ws) >> 5;
((uint32_t*)rp)[0] = rngi(ws);
r >>= 6ULL;
// Uncomment this line to make the proram work properly
//printf("0x%08X%08X\n", ((uint32_t*)rp)[1], ((uint32_t*)rp)[0]);
/* Create double precision floating point random number in the range [0,1)
The constant is generated as:
uint64_t g = 0x0020ULL;
printf("%0.24g \n",1.0/(*((double*)(&g;
*/
return *((double*)rp) * 2.24711641857789488466163e+307;
}
int main(void)
{
static uint32_t* ws = NULL;
double r = rng(ws);
printf("%g\n",r);
return 0;
}
-- System Information:
Debian Release: 4.0
APT prefers testing
APT policy: (500, 'testing')
Architecture: i386 (i686)
Shell: /bin/sh linked to /bin/bash
Kernel: Linux 2.6.20
Locale: LANG=en_GB, LC_CTYPE=sv_SE (charmap=ANSI_X3.4-1968) (ignored: LC_ALL
set to C)
Versions of packages gcc-4.1 depends on:
ii binutils2.17-3 The GNU assembler, linker and bina
ii cpp-4.1 4.1.1-21 The GNU C preprocessor
ii gcc-4.1-base4.1.1-21 The GNU Compiler Collection (base
ii libc6 2.3.6.ds1-11 GNU C Library: Shared libraries
ii libgcc1 1:4.1.1-21 GCC support library
ii libssp0 4.1.1-21 GCC stack smashing protection libr
Versions of packages gcc-4.1 recommends:
ii libc6-dev 2.3.6.ds1-11 GNU C Library: Development Librari
pn libmudflap0-dev(no description available)
-- no debconf information
--- End Message ---
--- Begin Message ---
Anders Johansson <[EMAIL PROTECTED]> writes:
> The below code should return a random number between 0 and 1, but does
> not do that when -O2 or higher is enabled. Uncomment the printf line
> to make the code work properly.
[...]
> uint64_t r = 0ULL;
> void* rp = &r;
> ((uint32_t*)rp)[1] = rngi(ws) >> 5;
This code accesses a value of type uint64_t by an lvalue of type
uint32_t. This is not allowed by C's aliasing rules. So the behavior
is undefined, and this is not a bug in gcc. See the documentation of
-fno-strict-aliasing.
--
Falk
--- End Message ---
Bug#410656: marked as done (gcc-4.1: Missing symbol `_Unwind_GetIPInfo' building with gcc -m32 on amd64.)
Your message dated Tue, 27 Feb 2007 11:25:45 + with message-id <[EMAIL PROTECTED]> and subject line Not a bug. has caused the attached Bug report to be marked as done. This means that you claim that the problem has been dealt with. If this is not the case it is now your responsibility to reopen the Bug report if necessary, and/or fix the problem forthwith. (NB: If you are a system administrator and have no idea what I am talking about this indicates a serious mail system misconfiguration somewhere. Please contact me immediately.) Debian bug tracking system administrator (administrator, Debian Bugs database) --- Begin Message --- Package: gcc-4.1 Version: 4.1.1-21 Severity: normal I'm trying to build the nspluginwrapper source on an amd64 machine. The x86_64 part builds okay, but when it goes to build the i386 runtime part with gcc -m32 the build is failing with the following error: $ make gcc -std=c99 -m32 -o npviewer.bin npviewer-npw-viewer.o npviewer-npw-rpc.o npviewer-rpc.o npviewer-debug.o npviewer-utils.o npviewer-npruntime.o npviewer-cxxabi-compat.o -m32 -Llsb-build-i386 -lgtk-x11-2.0 -lgdk-x11-2.0 -lgobject-2.0 -ldl -lglib-2.0 -lX11 -lXt -ldl -lpthread -Wl,--export-dynamic -Wl,--version-script,../src/npw-viewer.map -lsupc++ /usr/lib/gcc/x86_64-linux-gnu/4.1.2/32/libsupc++.a(eh_personality.o): In function `__gxx_personality_v0': (.text.__gxx_personality_v0+0xb8): undefined reference to `_Unwind_GetIPInfo' collect2: ld returned 1 exit status make: *** [npviewer.bin] Error 1 I've run through the list of gcc bugs and this is listed as a problem with gcc 4.2, but not with 4.1. (I've included the versions of the -i386 libc6 counterparts installed below) -- System Information: Debian Release: 4.0 APT prefers unstable APT policy: (500, 'unstable'), (1, 'experimental') Architecture: amd64 (x86_64) Shell: /bin/sh linked to /bin/bash Kernel: Linux 2.6.20 Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8) Versions of packages gcc-4.1 depends on: ii binutils2.17-3 The GNU assembler, linker and bina ii cpp-4.1 4.1.1-21 The GNU C preprocessor ii gcc-4.1-base4.1.1-21 The GNU Compiler Collection (base ii libc6 2.3.6.ds1-11 GNU C Library: Shared libraries ii libgcc1 1:4.1.1-21 GCC support library ii libssp0 4.1.1-21 GCC stack smashing protection libr ii libc6-i386 2.3.6.ds1-11 GNU C Library: 32bit shared librar Versions of packages gcc-4.1 recommends: ii libc6-dev 2.3.6.ds1-11 GNU C Library: Development Librari ii libmudflap0-dev 4.1.1-21 GCC mudflap support libraries (dev ii libc6-dev-i386 2.3.6.ds1-11 GNU C Library: 32bit development l -- no debconf information --- End Message --- --- Begin Message --- This was not a gcc bug. Closing. -- rob andrews :: pgp 0x01e00563 :: [EMAIL PROTECTED] --- End Message ---
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