我应该使用哪些gdb命令来缩小在“ main”标签中出现分段错误的位置？ [英] What gdb commands should I use to narrow down where in label 'main' did I get the segmentation fault?
问题描述
这是我的汇编代码和主要子例程。
这是我的宏和常量：
Here's my assembly code and my main subroutine. Here are my macros and constants:
.text
fmt: .string "x \t\t ln(x)\n"
sfmt: .string "%.10lf \t %.10lf\n"
error: .string "Error"
filename: .string "input.bin"
.data
LIM: .double 0r1.0E-13
zero: .double 0r0.0
one: .double 0r1.0
half: .double 0r0.5
define(i_r,w19)
define(j_r,w20)
define(n_r,w21)
define(fd_r,w22)
define(ln_x,d8)
define(cur_term,d24)
define(n_read,x25)
define(x_j,d26)
BUF_SIZE = 98*8
AT_FDCWD = -100
O_RDONLY = 0
buf_s = 16
.bss
x_arr: .skip BUF_SIZE
fp .req x29
lr .req x30
.balign 4
.global main
这是我的主要子程序：
main:
stp fp,lr,[sp,-16]!
mov fp,sp
ldp fp,lr,[sp],16
ret
我已经使用过gdb，但是它仅指出SIGSEGV信号来自main（）中的0x0000000000420358。如何缩小该信号在主要位置的位置？
PS我只知道GDB的基础知识。
I already used gdb however, it only points out that the SIGSEGV signal came from 0x0000000000420358 in main(). How can I narrow down where in 'main' this signal comes from? P.S I only know the basics of GDB.
GDB内容：（更新）
GDB Stuff:(update)
(gdb) x/i $pc
=> 0x420358: .inst 0x00000000 ; undefined
我不知道这是否有帮助，但这是C版本。我将其转换为程序集，因为那是我需要提交的内容。此外，由于多数民众赞成在作弊，因此我们无法使用任何类型的转换器。
I don't know if this helps but this is the C version THAT WORKS. I am converting it to assembly because thats what I need to hand in. Also we cannot use any types of converter since thats considered cheating.
#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h> //Used for the keyword for flags and other predefined values for the argument on openat,etc.
#define LIM 1.0e-13
#define DOUBSIZE 100 //There are 97 double values in the binary file
#define buf_size 98*8
double x[DOUBSIZE];
int main() {
register int i = 1,j = 0,fd = openat(AT_FDCWD,"input.bin",O_RDONLY); //int fd = openat(int dirfd,const char *pathname (basically a string),int flags,mode_t mode);
register double ln_x = 0.0,cur_term;
//double *x; //(only local variable) //(a local variable so it must be in the stack)only assuming there are 32 double precision values in the binary file
register long n_read = read(fd,&x,buf_size); //reads in 8 bytes(lost the double x[...] in this line since x is now pointing at the buffer
if(fd == -1) {
printf("Error!");
return 0;
}
if(n_read == -1) { //Error checker
printf("Error!");
return 0;
}
printf("x \t\t ln(x)\n"); //The header of the thing to be printed
while(j < (buf_size/8)) { //note that it is implied that EOF = -1 in C
if(x[j] <= 0.5) { //if x is less than or equal to 1/2,go to the next double value(assuming I don't know values in the bin file)
j++;
i = 1;
continue;
}
cur_term = (1.0/i) * (pow((double)((x[j]-1.0)/(x[j])),i));
ln_x += cur_term;
while(cur_term >= LIM) { //continue to accumulate terms until the absolute value of the term is less than 1.0E-13
i++; //follows the pattern of the series.
cur_term = (1.0/i)*(pow((double)((x[j]-1.0)/(x[j])),i)); //since it should start with x[1]
ln_x += cur_term; //adds the new term to previous ln(x) value
}
printf("%.10lf \t %.10lf\n",x[j],ln_x); //prints the current value of ln(x) and x
j++; //manages which x double value will be used next
i = 1;
ln_x = 0.0;
}
close(fd);
return 0;
}
推荐答案
列出您的 main 位于 .bss 部分，而不是 .text ，因此只能包含全零字节。 （而且它将无法执行。）
Turns out your main is in the .bss section, not .text where it belongs, so it can only contain all-zero bytes. (And it won't be executable).
GDB通常只想反汇编 .text 部分中的代码。
GDB normally only wants to disassemble code in the .text section so that also explains GDB being weird.
这就是为什么您应该将代码简化为MCVE（ Minimal / complete / verifiable example）的原因使它尽可能小，同时仍能解决问题。
This is why you should reduce your code to a MCVE (Minimal / complete / verifiable example) to make it as small as possible while still containing the problem.
这篇关于我应该使用哪些gdb命令来缩小在“ main”标签中出现分段错误的位置？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
