goto

问题 I found the following code in a C program: while (1) { do_something(); if (was_an_error()) break; do_something_else(); if (was_an_error()) break; [...] break; } [cleanup code] Here while(1) is used as local emulation of "finally". You can also write this using goto s: do_something() if (was_an_error()) goto out; do_something_else() if (was_an_error()) goto out; [...] out: [cleanup code] I thought the goto solution is a usual idiom. I have seen several occurrences of this idiom in the kernel

问题 We are writing a byte-code for a high-level compiled language, and after a bit of profiling and optimization, it became clear that the current largest performance overhead is the switch statement we're using to jump to the byte-code cases. We investigated pulling out the address of each case label and storing it in the stream of byte-code itself, rather than the instruction ID that we usually switch on. If we do that, we can skip the jump table, and directly jump to the location of code of

问题 I am trying:- To re-read the value if user enters an invalid value. But the problem is scanf() executes only once and won't execute any other time and programs gets stuck with an infinite loop. #include<stdio.h> #include<math.h> main() { unsigned int a; unsigned int b = pow(2,M-1); unsigned int c; int x; printf("b = %i",b); input: fflush(stdin); fflush(stdout); printf("\nEnter any integer: "); x = scanf("%u",&a); printf("%u",a); if(x==0) goto input; printf("\na = %i",a); c = a & b; printf("

问题 I've long been under the impression that goto should never be used if possible. While perusing libavcodec (which is written in C) the other day, I noticed multiple uses of it. Is it ever advantageous to use goto in a language that supports loops and functions? If so, why? 回答1: There are a few reasons for using the "goto" statement that I'm aware of (some have spoken to this already): Cleanly exiting a function Often in a function, you may allocate resources and need to exit in multiple places

问题 I've long been under the impression that goto should never be used if possible. While perusing libavcodec (which is written in C) the other day, I noticed multiple uses of it. Is it ever advantageous to use goto in a language that supports loops and functions? If so, why? 回答1: There are a few reasons for using the "goto" statement that I'm aware of (some have spoken to this already): Cleanly exiting a function Often in a function, you may allocate resources and need to exit in multiple places

问题 Is it true that goto jumps across bits of code without calling destructors and things? e.g. void f() { int x = 0; goto lol; } int main() { f(); lol: return 0; } Won't x be leaked? 回答1: Warning: This answer pertains to C++ only ; the rules are quite different in C. Won't x be leaked? No, absolutely not. It is a myth that goto is some low-level construct that allows you to override C++'s built-in scoping mechanisms. (If anything, it's longjmp that may be prone to this.) Consider the following

问题 Closed . This question needs to be more focused. It is not currently accepting answers. Want to improve this question? Update the question so it focuses on one problem only by editing this post. Closed 5 years ago . Locked . This question and its answers are locked because the question is off-topic but has historical significance. It is not currently accepting new answers or interactions. In this thread, we look at examples of good uses of goto in C or C++. It's inspired by an answer which

问题 Closed . This question needs details or clarity. It is not currently accepting answers. Want to improve this question? Add details and clarify the problem by editing this post. Closed 6 years ago . # include <stdio.h> int main() { int a=5; begin: if(a) printf("%d\n",a); a--; goto begin; return 0; } When a becomes 0 then if condition will not execute then why the output is going to be infinty in this code means output - 5 4 3 2 1 0 -1 -2 and so on endless 回答1: If the program really does print

问题 I have folders like E:\Backups\code\Hazard\test1 ... testn And inside these test folders something like E:\Backups\code\Hazard\test1\it0 ... itn The root folder is E:\Backups\code from where the code runs. The below code runs on each subfolders and copies summary.yml from it0 folder to latest it(n) folder. Why the code runs just for test1 folder and then hangs? setlocal ENABLEDELAYEDEXPANSION set root=%cd% for /D %%X in (%root%\*) do ( echo %%X cd %%X for /D /r %%b in (*) do ( cd %%b echo %%b

问题 How to go back to menu using case in switch case without using GOTO command. So this is the sample: while(1){ printf("1: Basic Math\n2. Intermediate Math\n3. Advance Math"); printf("Enter your choice: "); int choice; scanf("%d", &choice); switch(choice) int theChoices; case 1: printf("1. Add\n 2. Subtract\n3. Go back to menu"); scanf("%d", &theChoices); switch (theChoices) { case 1: //calculation ... case 2: //calculation ... case 3: // Go Back to menu which is Basic math, Intermediate Math,