是否有GCC宏来确定未消除框架指针?

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问题描述

使用-fomit -frame -pointer(用于各种-O设置)时，执行回溯是有问题的.我想知道是否有一种在编译时间确定使用此开关的代码的方法?在这种情况下，我可以放入#ifndef时要在不明智的情况下防止回避.

此-Fomit-Fomit-Fame-Pointer Switch已打开?

谢谢，

setJMP

其他推荐答案

您不能在编译时执行此操作，但是在运行时您可以检查程序是否优化.

编写一个肯定会通过优化器更改的代码，例如将非挥发变量与setjmp/longjmp混合，并且通过该变量的值，您将知道您的程序是否已优化.

#include <setjmp.h>
#include <stdio.h>

int is_optimised(void) {
    int i = 1;
    jmp_buf jmp_loc;

    if (setjmp(jmp_loc)) {
        return i;  // optimiser changes it to "return 1"
    }

    i = 0;
    longjmp(jmp_loc, 1);

    return 0;
}

int main(int argc, char *argv[]) {
    printf("%soptimised\n", is_optimised() ? "" : "non-");

    return 0;
}

如果使用GCC编译，没有-O开关打印" non-optimised"，则为-O1 to -O4它打印" optimised".

当然您的里程(与其他编译器)可能会有所不同.

其他推荐答案

至于检查时，在运行时检查EBP寄存器(调整您的体系结构)是否指向堆栈顶部的几个字节，然后遵循存储在[EBP]的指针是有道理的.

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问题描述

When -fomit-frame-pointer is used (automatic for various -O settings), performing a backtrace is problematic. I am wondering if there is a way of determining at compile time that the code is compiled with this switch? In that case, I could put in an #ifndef to guard against backtracing when ill-advised.

Is any macro set when this -fomit-frame-pointer switch is on?

Thanks,

SetJmp

其他推荐答案

You cannot do it at compile time, but at runtime you can check whether your program optimised or not.

Write a code that definitely will be changes by optimiser, like mixing non-volatile variable with setjmp/longjmp, and by the value of that variable you will know whether your program is optimised or not.

#include <setjmp.h>
#include <stdio.h>

int is_optimised(void) {
    int i = 1;
    jmp_buf jmp_loc;

    if (setjmp(jmp_loc)) {
        return i;  // optimiser changes it to "return 1"
    }

    i = 0;
    longjmp(jmp_loc, 1);

    return 0;
}

int main(int argc, char *argv[]) {
    printf("%soptimised\n", is_optimised() ? "" : "non-");

    return 0;
}

If compiled with GCC without -O switch it prints "non-optimised", for switches -O1 to -O4 it prints "optimised".

Of course your mileage (with other compilers) may vary.

其他推荐答案

As for the check, at runtime check if ebp register (adjust for your architecture) points to a few bytes below the top of the stack and then if following the pointer stored at [ebp] makes sense.

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