Linux 的 function 追踪
在学习开源代码或者接触到老项目的时候，对于复杂的函数调用流程，往往会感觉晕头转向。这个时候如果能打印出函数的执行流程，对于我们了解项目会很有帮助，下面介绍一下在Linux下打印函数调用流程的技术。
1. 使用gcc和g++的 -finstrument-functions 选项
-finstrument-functions 选项的意思是在函数的入口处自动的插入 __cyg_profile_func_enter 在函数的出口自动加入 __cyg_profile_func_exit ，通过自己实现这两个函数，就可以打印出调用流程了。
2. function_trace.c
实现的一个模板如下:
//function_trace.c
#include <stdio.h>
#define __USE_GNU
#include <dlfcn.h>
static FILE *fp_trace=NULL;
static int nDepth = 0;
void __cyg_profile_func_enter(void *func, void *caller) __attribute__((no_instrument_function));
void __cyg_profile_func_exit(void *func, void *caller) __attribute__((no_instrument_function));
void __attribute__((constructor)) traceBegin(void) {
fp_trace = fopen("func_trace.out", "w");
}
void __attribute__((destructor)) traceEnd(void) {
if (fp_trace != NULL) {
fclose(fp_trace);
fp_trace = NULL;
}
}
void __cyg_profile_func_enter(void *func, void *caller)
{
nDepth ++;
for(int i = 0 ; i nDepth ; i++)
{
if(fp_trace)
{
fprintf(fp_trace,"\t");
}
printf("\t");
}
Dl_info info;
if (dladdr(func, &info) != 0)
{
if(fp_trace)
{
fprintf(fp_trace,"Enter:[%s,%s] \n",info.dli_fname,info.dli_sname);
}
printf("Enter:[%s,%s] \n",info.dli_fname,info.dli_sname);
}
}
void __cyg_profile_func_exit(void *func, void *caller) {
for(int i = 0 ; i nDepth ; i++)
{
if(fp_trace)
{
fprintf(fp_trace,"\t");
}
printf("\t");
}
nDepth --;
Dl_info info;
if (dladdr(func, &info) != 0)
{
if(fp_trace)
{
fprintf(fp_trace,"Enter:[%s,%s] \n",info.dli_fname,info.dli_sname);
}
printf("Leave:[%s,%s] \n",info.dli_fname,info.dli_sname);
}
}
编译命令:
gcc function_trace.c -c
3 主文件示例
functrace_main.cpp
//functrace_main.cpp
#include <stdio.h>
class CBase
{
public:
explicit CBase()
{
}
virtual ~CBase()
{
}
virtual void Print()
{
printf("%s\n",__PRETTY_FUNCTION__);
}
};
class CDriveOne:public CBase
{
public:
CDriveOne()
{
}
virtual ~CDriveOne()
{
}
virtual void Print() override
{
printf("%s\n",__PRETTY_FUNCTION__);
}
};
class CDriveTwo:public CBase
{
public:
CDriveTwo()
{
}
virtual ~CDriveTwo()
{
}
virtual void Print() override
{
printf("%s\n",__PRETTY_FUNCTION__);
}
};
void Overload()
{
printf("%s\n",__PRETTY_FUNCTION__);
}
void Overload(int x)
{
printf("%s\n",__PRETTY_FUNCTION__);
}
void FuncOuter()
{
}
void FuncMedium()
{
FuncOuter();
}
void FuncInner()
{
FuncOuter();
FuncMedium();
}
int main(int argc, char **argv) {
{
printf("----------------------------Drive override Test Begin\n");
CBase * pFirst = new CDriveOne();
pFirst->Print();
CBase * pSecond = new CDriveTwo();
pSecond->Print();
delete pFirst;
delete pSecond;
printf("----------------------------Drive override Test End\n");
}
{
printf("----------------------------Override Test Begin\n");
Overload();
Overload(2);
printf("----------------------------Override Test End\n");
}
{
printf("----------------------------Simple Test Begin\n");
FuncOuter();
FuncMedium();
FuncInner();
printf("----------------------------Simple Test End\n");
}
return 0;
}
编译命令:
g++ -g function_trace.o functrace_main.cpp -ldl -finstrument-functions -export-dynamic
4 程序输出
Enter:[./a.out,main]
----------------------------Drive override Test Begin
Enter:[./a.out,_ZN9CDriveOneC1Ev]
Enter:[./a.out,_ZN5CBaseC1Ev]
Leave:[./a.out,_ZN5CBaseC1Ev]
Leave:[./a.out,_ZN9CDriveOneC1Ev]
Enter:[./a.out,_ZN9CDriveOne5PrintEv]
virtual void CDriveOne::Print()
Leave:[./a.out,_ZN9CDriveOne5PrintEv]
Enter:[./a.out,_ZN9CDriveTwoC2Ev]
Enter:[./a.out,_ZN5CBaseC1Ev]
Leave:[./a.out,_ZN5CBaseC1Ev]
Leave:[./a.out,_ZN9CDriveTwoC2Ev]
Enter:[./a.out,_ZN9CDriveTwo5PrintEv]
virtual void CDriveTwo::Print()
Leave:[./a.out,_ZN9CDriveTwo5PrintEv]
Enter:[./a.out,_ZN9CDriveOneD0Ev]
Enter:[./a.out,_ZN9CDriveOneD2Ev]
Enter:[./a.out,_ZN5CBaseD2Ev]
Leave:[./a.out,_ZN5CBaseD2Ev]
Leave:[./a.out,_ZN9CDriveOneD2Ev]
Leave:[./a.out,_ZN9CDriveOneD0Ev]
Enter:[./a.out,_ZN9CDriveTwoD0Ev]
Enter:[./a.out,_ZN9CDriveTwoD1Ev]
Enter:[./a.out,_ZN5CBaseD2Ev]
Leave:[./a.out,_ZN5CBaseD2Ev]
Leave:[./a.out,_ZN9CDriveTwoD1Ev]
Leave:[./a.out,_ZN9CDriveTwoD0Ev]
----------------------------Drive override Test End
----------------------------Override Test Begin
Enter:[./a.out,_Z8Overloadv]
void Overload()
Leave:[./a.out,_Z8Overloadv]
Enter:[./a.out,_Z8Overloadi]
void Overload(int)
Leave:[./a.out,_Z8Overloadi]
----------------------------Override Test End
----------------------------Simple Test Begin
Enter:[./a.out,_Z9FuncOuterv]
Leave:[./a.out,_Z9FuncOuterv]
Enter:[./a.out,_Z10FuncMediumv]
Enter:[./a.out,_Z9FuncOuterv]
Leave:[./a.out,_Z9FuncOuterv]
Leave:[./a.out,_Z10FuncMediumv]
Enter:[./a.out,_Z9FuncInnerv]
Enter:[./a.out,_Z9FuncOuterv]
Leave:[./a.out,_Z9FuncOuterv]
Enter:[./a.out,_Z10FuncMediumv]
Enter:[./a.out,_Z9FuncOuterv]
Leave:[./a.out,_Z9FuncOuterv]
Leave:[./a.out,_Z10FuncMediumv]
Leave:[./a.out,_Z9FuncInnerv]
----------------------------Simple Test End
Leave:[./a.out,main]
``` /pre>
输出分析:
```console
Enter:[./a.out,_ZN9CDriveOneC1Ev] //派生类 ```CDriveOne ```的构造函数 br />
Enter:[./a.out,_ZN5CBaseC1Ev] //父类 ```CBase ```的构造函数
Enter:[./a.out,_Z8Overloadv] //调用 ```void Overload() ``` br />
Enter:[./a.out,_Z8Overloadi] //调用 ```void Overload(int) ```