Use gdb within Emacs: always show the source code

Question

I'm a Vim user and don't know much about Emacs. I'm interested with Emacs because I find that debugging within Emacs is more pleasant. For example, it provides syntax highlighting and I can set breakpoints with the mouse.

Everything works well except when printf is encountered.

Simple code for illustration:

1 #include <stdio.h>
2 
3 int main()
4 {
5     int a = 1;
6     printf("%d\n", a);
7     int b = 2;
8     return 0;
9 }

emacs main.c
left click on the bottom half
M-x gdb[return][return]
(gdb) b 6
(gdb) r

By now, the source codes are showed in the upper half, and gdb prompt in the bottom half. This is exactly what I want.

(gdb) n

Now the source codes disappear, and the upper half is used to show stdout instead. This is really inconvenient. I'd like the stdout to show in the gdb buffer, and the sources stay in the upper buffer, just as the gdb -tui mode.

Chris Chris · Accepted Answer · 2014-06-24T13:02:47

Instead of manually setting up your splits each time, try telling GDB which windows you want available.

For example:

;; Show main source buffer when using GDB
(setq gdb-show-main t)

Now you can simply use M-x gdb to start GDB, and it should keep your source code buffer displayed in a split window.

Incidentally, Emacs' GDB interface supports a number of other windows that you may want to enable:

If gdb-many-windows is non-nil, then M-x gdb displays the following frame layout:
+--------------------------------+--------------------------------+
|   GUD interaction buffer       |   Locals/Registers buffer      |
|--------------------------------+--------------------------------+
|   Primary Source buffer        |   I/O buffer for debugged pgm  |
|--------------------------------+--------------------------------+
|   Stack buffer                 |   Breakpoints/Threads buffer   |
+--------------------------------+--------------------------------+
If you ever change the window layout, you can restore the "many windows" layout by typing M-x gdb-restore-windows. To toggle between the many windows layout and a simple layout with just the GUD interaction buffer and a source file, type M-x gdb-many-windows.

You may also specify additional GDB-related buffers to display, either in the same frame or a different one. Select the buffers you want by typing M-x gdb-display-BUFFERTYPE-buffer or M-x gdb-frame-BUFFERTYPE-buffer, where BUFFERTYPE is the relevant buffer type, such as breakpoints. You can do the same with the menu bar, with the GDB-Windows and GDB-Frames sub-menus of the GUD menu.

When you finish debugging, kill the GUD interaction buffer with C-x k, which will also kill all the buffers associated with the session. However you need not do this if, after editing and re-compiling your source code within Emacs, you wish to continue debugging. When you restart execution, GDB automatically finds the new executable. Keeping the GUD interaction buffer has the advantage of keeping the shell history as well as GDB's breakpoints. You do need to check that the breakpoints in recently edited source files are still in the right places.

Use gdb within Emacs: always show the source code

2 Answers