[英]compiling error “impossible constraint in 'asm'”
我試圖在“ SunOS sun4v 5.10”系統上編譯Csmith,但是出現了以下錯誤:
platform.cpp: In function 'long unsigned int platform_gen_seed()':
platform.cpp:78: error: impossible constraint in 'asm'
誰能說出錯誤在哪里?
#if (TARGET_CPU_powerpc == 1 || TARGET_CPU_powerpc64 == 1)
/*For PPC, got from:
http://lists.ozlabs.org/pipermail/linuxppc-dev/1999-October/003889.html
*/
static unsigned long long read_time(void) {
unsigned long long retval;
unsigned long junk;
__asm__ __volatile__ ("\n\
1: mftbu %1\n\
mftb %L0\n\
mftbu %0\n\
cmpw %0,%1\n\
bne 1b"
: "=r" (retval), "=r" (junk));
return retval;
}
#else
#ifdef WIN32
static unsigned __int64 read_time(void) {
unsigned l, h;
_asm {rdtsc
mov l, eax
mov h, edx
}
return (h << 32) + l ;
}
#else
static long long read_time(void) {
long long l;
asm volatile( "rdtsc\n\t"
: "=A" (l)
);
return l;
}
#endif
#endif
unsigned long platform_gen_seed()
{
return (long) read_time();
}
問題在於,您要編譯的代碼假定所有不是PowerPC的目標CPU都必須是x86處理器。 該代碼根本不支持您的SPARC CPU。
幸運的是,該代碼似乎並不關鍵,它顯然僅用於播種隨機數生成器,然后用於創建隨機C程序。 目的是防止同時啟動的程序的多個實例生成相同的隨機程序。 我將用不依賴於CPU的更具移植性的代碼替換代碼。 像這樣:
#ifdef WIN32
unsigned long platform_gen_seed()
{
LARGE_INTEGER now;
QueryPerformanceCounter(&now);
return now.LowPart;
}
#else /* assume something Unix-like */
static unsigned long generic_gen_seed() {
pid_t pid = getpid();
time_t now;
time(&now);
return (unsigned long)(now ^ (pid << 16 | ((pid >> 16) & 0xFFFF)));
}
#ifdef CLOCK_REALTIME
unsigned long platform_gen_seed()
{
struct timespec now, resolution;
if (clock_gettime(CLOCK_REALTIME, &now) == -1
|| clock_getres(CLOCK_REALTIME, &resolution) == -1
|| resolution.tv_sec > 0 || resolution.tv_nsec > 1000000) {
return generic_gen_seed();
}
return (now.tv_nsec / resolution.tv_nsec
+ now.tv_sec * resolution.tv_nsec);
}
#else
unsigned long platform_gen_seed()
{
return generic_gen_seed();
}
#endif /* CLOCK_REALTIME */
#endif /* WIN32 */
該代碼已在Linux和Windows上進行了單獨測試。 它也應該在Solaris SPARC上獨立工作,但是我不知道它在實際程序中的運行情況如何。
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