Several ways to add breakpoints using GDB

1. Normal breakpoints

Setting breakpoints based on the number of lines of code is the most common way , stay debug Breakpoints can be configured before the program runs . Such as ：

(gdb) b src/main.cpp:127

When the program is executed to main.cpp File first 127 The breakpoint will be triggered when the line .

2. Conditional breakpoints

seeing the name of a thing one thinks of its function , This breakpoint is triggered when certain conditions are met , It is more suitable for abnormal troubleshooting . Setting mode (gdb)break line-or-function if (condition), Such as ：

(gdb) b src/main.cpp:127 if cnt==10

3. Data breakpoints

Is to set the breakpoint according to the address , It can only be in debug After the program runs, set , Because only after running , You can easily get the address of the variable . A breakpoint is triggered when the content of the address changes . There are two ways to set data breakpoints , One is to directly point out the address value , Such as ：

(gdb) b *0x400522

Note that it must be added * Number . The way to get the address value is , Set the normal breakpoint first , At the breakpoint print & Variable name You can get the address of the variable . The other, of course, is to directly set the variable name , Such as ：

(gdb) b & Variable name 

4. Function breakpoints

This kind of breakpoint is a breakpoint that will be triggered when the program executes to a program . The setting method is as follows: ：

(gdb) b funcName

But function breakpoints are not valid for all functions , Such as optimized static functions and inline Functions, etc , You may not be able to trigger breakpoints .

5. monitor

Setting monitoring must also be done after the program runs . Such as ：

(gdb) watch * Address     #  When the content referred to by the address changes, the breakpoint 

(gdb) watch var    # When var When the value changes , The breakpoint 

(gdb) watch (condition)    # When the conditions are met , The breakpoint 

Monitoring is also known as hardware breakpoints . You can monitor the changes of stack variables and heap variables , When the value of the monitored variable changes , The program was stopped .