Linux GDB Learning

Gdb

The GCC compilation option plus –g adds debug information to the generated target code.

Gcc–g–o Hello hello.c

Redhat 6.3 Default is not to install GDB, if installed from the system CD (iOS image file), unzip it in the Packages folder to find gdb-7.2-56.el6.i686.rpm, and then execute the following command:

RPM-IVH gdb-7.2-56.el6.i686.rpm (because different numbers of versions may differ)

1. Start GDB

directive: GDB program name [Corefile]

Corefile is optional, but it enhances GDB's ability to debug

Linux does not generate the Corefile file by default, so you need to add the same code in the. bashrc file Ulimit–c Unlimited the. bashrc file is in the host directory (after modifying the play. bashrc file, remember to execute: BASHRC let the changes take effect)

Corefile file saves the program's memory information when the program is running in error (GDB debugging is run-time error , code error is the compiler)

Write a wrong procedure first:

To compile it

compiler does not have an error

And look at the time it runs.

The program makes an error by manipulating a null pointer, and produces a corefile file in the current directory

Now combine corefile with GDB for debugging

Plus corefile can know the wrong information, and where the code where the error occurred, without adding corefile, such as

There is no error message, the program requires you to step-by-step debugging and then find the error.

2. GDB Common Command Run

Let the program run directly, knowing that a breakpoint or error has been encountered

GDB can see the memory information of the program error, 0X000000004004D4 represents the memory address.

where

What's wrong with the test () function? Where command, displays the execution function tree that caused the segment error

This is the order of the function calls, and number No. 0 represents the current function. Number 1th means that the main function calls the test function, so test is number 0th, and main is the order of the call function is saved by the stack.

List

List[m,n], m/n is the first M-line and the last N-row to display where the error code appears. Show nearby 10 rows without parameters

Whatis

What type of query variable is a rule with print

Print

one of the most useful features of GDB is that it can display the values of any expression, variable in the program being debugged

Print variable \ Expression

print ' file ':: variable \ expression, ' is required to let gdb know that it refers to a file name

Print FuncName:: variable, expression

PType

PType tells you the structure of the definition, note is the structure of the body

Break

The break command sets a breakpoint:

Breaklinenum

Breakfuncname

Breakfilename::linenum

Breakfilename:funcname

Well, this can be translated and understood.

Infobreak Viewing breakpoint information

Continue run to the next breakpoint

Delete Deletes all breakpoints, delete num Deletes the breakpoint of the specified label

Set Variable

setvariable Changing the value of a variable

SetVariable varname = value

Single Step Commissioning Step Next

Step only runs the line code compared to continue step, and step enters the function when it encounters the function.

Next is equal to step but does not enter the function, but runs to the next line

Return stops executing the current function, saying that value is returned to the caller, and step jumps out with return when running inside the function

Linux GDB Learning