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diff --git a/md/writeup/fpu_catch_division_by_zero.md b/md/writeup/fpu_catch_division_by_zero.md new file mode 100644 index 0000000..a27cd75 --- /dev/null +++ b/md/writeup/fpu_catch_division_by_zero.md @@ -0,0 +1,56 @@ +title:FPU catch division by zero +keywords:fpu,zero,c,assembler,cpu + +# FPU catch division by zero +There can occure some problems in C onw of them is divison on zero. +For this we setup system exception handler or signal handler. +When is division on zero it works.Also for return in main function +there is used setjmp and longjmp + +```c +void set_exception_handler() +{ + int err; + fenv.__control_word &= ~FE_ALL_EXCEPT; + fenv.__cs_selector &= ~FE_ALL_EXCEPT << 7; + fesetenv( &fenv ); + + sa.sa_sigaction = &exception_handler; + sa.sa_flags = SA_SIGINFO; + err = sigaction( SIGFPE, &sa, NULL ); + if (err != 0) + printf("Cannot set FloatingPoint exception handler\n"); + else + printf("[OK] SIGFPE is set\n"); +} + +void exception_handler(int i, siginfo_t *s, void *v ) +{ + if (s->si_signo == SIGFPE) + { + printf("[SIGFPE] SIGFPE Occure\n"); + printf("[SIGFPE] Error number: %d\n", s->si_errno); + printf("[SIGFPE] Signal code: %d\n", s->si_code); + switch (s->si_code) + { + case FPE_INTDIV: + printf("[SIGFPE] Divison by 0\n"); + longjmp( jmp , 1 ); + break; + } + } + abort(); +} +``` + +Compilation is easy: +``` +gcc sigfpe.c -o sigfpe -lm +``` +Now it will no so big problem when some error occur to properly exit +or make some checks. + + +## Downloads +exception_in_c.zip - +2KiB - http://archive.main.lv/files/writeup/fpu_catch_division_by_zero/exception_in_c.zip
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