Package: gcc-4.3
Version: 4.3.2-1.1
Severity: normal
Test program:
/* compile with gcc -m32 -O2 -lm */
extern int feenableexcept(int);
typedef union { double num; int tag[2]; } naRef;
int naStr_len(naRef r) __attribute__((noinline));
int naStr_len(naRef r) { return 0; }
volatile int use_num;
static int equal(naRef a, naRef b)
{
if (use_num) return a.num == b.num;
if (naStr_len(a) != naStr_len(b)) return 0;
return 1;
}
int findcell(naRef *hr, naRef key, int len)
{
int i;
for (i = 0; i < len; i++)
if (equal(key, hr[i]))
return i;
return 0;
}
int main(int argc, char* argv[])
{
naRef hr;
naRef key;
feenableexcept(13);
key.tag[0] = 0;
key.tag[1] = 0x7ff56789;
hr = key;
use_num = 0;
return findcell(&hr, key, use_num + 1);
}
/* end of test program */
Compiling the above program either with native 32 bit gcc or the 32
bit mode of the 64 bit compiler with -O2 optimization generates code
that will crash with a floating point exception.
Studying the assembly code, apparently gcc uses fld/fstp to copy the
"key" argument in the "findcell" function. It does that before
consulting the use_num variable. The value set in the "tag" member
unfortunately corresponds to a NaN in the "num" member, hence the
exception.
findcell:
pushl %ebp
movl %esp, %ebp
pushl %edi
pushl %esi
pushl %ebx
subl $28, %esp
movl 20(%ebp), %edi
testl %edi, %edi
jle .L4
fldl 12(%ebp)
xorl %esi, %esi
fstpl -32(%ebp) # <---- FAULT
Version 4.2.4 not affected, 4.4 series and trunk reported by others as affected.
-- System Information:
Debian Release: 5.0.3
APT prefers stable
APT policy: (500, 'stable')
Architecture: amd64 (x86_64)
Kernel: Linux 2.6.28.9 (SMP w/2 CPU cores)
Locale: LANG=C, LC_CTYPE=C (charmap=ANSI_X3.4-1968)
Shell: /bin/sh linked to /bin/bash
Versions of packages gcc-4.3 depends on:
ii binutils 2.18.1~cvs20080103-7 The GNU assembler, linker and bina
ii cpp-4.3 4.3.2-1.1 The GNU C preprocessor
ii gcc-4.3-base 4.3.2-1.1 The GNU Compiler Collection (base
ii libc6 2.7-18 GNU C Library: Shared libraries
ii libgcc1 1:4.3.2-1.1 GCC support library
ii libgomp1 4.3.2-1.1 GCC OpenMP (GOMP) support library
Versions of packages gcc-4.3 recommends:
ii libc6-dev 2.7-18 GNU C Library: Development Librari
Versions of packages gcc-4.3 suggests:
pn gcc-4.3-doc <none> (no description available)
pn gcc-4.3-locales <none> (no description available)
ii gcc-4.3-multilib 4.3.2-1.1 The GNU C compiler (multilib files
pn libgcc1-dbg <none> (no description available)
pn libgomp1-dbg <none> (no description available)
pn libmudflap0-4.3-dev <none> (no description available)
pn libmudflap0-dbg <none> (no description available)
-- no debconf information
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