実行中
double result = pow(base, exponent);
任意のbase
およびexponent
を使用
値が大きすぎたり複雑すぎたりする可能性があります。
たとえば、base=-2
、exponent=.5
(-2の平方根)
result==NAN
またはresult==HUGE_VAL
?
そのコードはC99に準拠し、クロスプラットフォームになりますか?
SIGFPEを捕まえて騒々しく死ぬ。クラッシュしたプログラムよりも悪いことがあります。それは、静かに間違った答えを出すプログラムです。
以下のサンプルコードが取得されます SIGFPEに関するランダムなサイトから
/* demo_SIGFPE.c
Demonstrate the generation of the SIGFPE signal.
Usage: demo_SIGFPE [optstr]
The main program executes code the generates a SIGFPE signal. Before doing
so, the program optionally ignores and/or blocks SIGFPE. If 'optstr'
contains 'i', then SIGFPE is ignored, otherwise it is caught by a handler.
If 'optstr' contains 'b', then SIGFPE is blocked before it is delivered.
The behavior that occurs when SIGFPE is generated depends on the kernel
version (Linux 2.6 is different from Linux 2.4 and earlier).
NOTE: Don't compile this program with optimization, as the arithmetic
below is likely to be optimized away completely, with the result that
we don't get SIGFPE at all.
*/
#define _GNU_SOURCE /* Get strsignal() declaration from <string.h> */
#include <string.h>
#include <signal.h>
static void
sigfpeCatcher(int sig)
{
printf("Caught signal %d (%s)\n", sig, strsignal(sig));
/* UNSAFE (see Section 21.1.2) */
sleep(1); /* Slow down execution of handler */
}
int
main(int argc, char *argv[])
{
int x, y;
sigset_t blockSet, prevMask;
Boolean blocking;
struct sigaction sa;
/* If no command-line arguments specified, catch SIGFPE, else ignore it */
if (argc > 1 && strchr(argv[1], 'i') != NULL) {
printf("Ignoring SIGFPE\n");
if (signal(SIGFPE, SIG_IGN) == SIG_ERR)
errExit("signal");
} else {
printf("Catching SIGFPE\n");
sigemptyset(&sa.sa_mask);
sa.sa_flags = SA_RESTART;
sa.sa_handler = sigfpeCatcher;
if (sigaction(SIGFPE, &sa, NULL) == -1)
errExit("sigaction");
}
blocking = argc > 1 && strchr(argv[1], 'b') != NULL;
if (blocking) {
printf("Blocking SIGFPE\n");
sigemptyset(&blockSet);
sigaddset(&blockSet, SIGFPE);
if (sigprocmask(SIG_BLOCK, &blockSet, &prevMask) == -1)
errExit("sigprocmask");
}
printf("About to generate SIGFPE\n");
y = 0;
x = 1 / y;
y = x; /* Avoid complaints from "gcc -Wunused-but-set-variable" */
if (blocking) {
printf("Sleeping before unblocking\n");
sleep(2);
printf("Unblocking SIGFPE\n");
if (sigprocmask(SIG_SETMASK, &prevMask, NULL) == -1)
errExit("sigprocmask");
}
printf("Shouldn't get here!\n");
exit(EXIT_FAILURE);
}