From 8142972d870f24ae9683238889aa63bb395d3698 Mon Sep 17 00:00:00 2001 From: Warren Young Date: Wed, 1 May 2013 23:30:25 +0000 Subject: Modernized user guide, API reference, and FAQ generation. Overall effect is to move away from DocBook SGML and DJ Delorie's doctool and toward pure DocBook XSL. (There remains just one use of doctool, and we have plans for replacing it, too.) See ChangeLog for details. --- winsup/doc/gdb.xml | 88 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 88 insertions(+) create mode 100644 winsup/doc/gdb.xml (limited to 'winsup/doc/gdb.xml') diff --git a/winsup/doc/gdb.xml b/winsup/doc/gdb.xml new file mode 100644 index 000000000..af0c0dd8a --- /dev/null +++ b/winsup/doc/gdb.xml @@ -0,0 +1,88 @@ + + + +Debugging Cygwin Programs + +When your program doesn't work right, it usually has a "bug" in +it, meaning there's something wrong with the program itself that is +causing unexpected results or crashes. Diagnosing these bugs and +fixing them is made easy by special tools called +debuggers. In the case of Cygwin, the debugger +is GDB, which stands for "GNU DeBugger". This tool lets you run your +program in a controlled environment where you can investigate the +state of your program while it is running or after it crashes. +Crashing programs sometimes create "core" files. In Cygwin these are +regular text files that cannot be used directly by GDB. + + +Before you can debug your program, you need to prepare your +program for debugging. What you need to do is add +-g to all the other flags you use when compiling +your sources to objects. + +Compiling with -g + +bash$ gcc -g -O2 -c myapp.c +bash$ gcc -g myapp.c -o myapp + + + +What this does is add extra information to the objects (they get +much bigger too) that tell the debugger about line numbers, variable +names, and other useful things. These extra symbols and debugging +information give your program enough information about the original +sources so that the debugger can make debugging much easier for +you. + +To invoke GDB, simply type gdb myapp.exe at the +command prompt. It will display some text telling you about itself, +then (gdb) will appear to prompt you to enter +commands. Whenever you see this prompt, it means that gdb is waiting +for you to type in a command, like run or +help. Oh :-) type +help to get help on the commands you can type in, or +read the GDB User's Manual for a complete +description of GDB and how to use it. + +If your program crashes and you're trying to figure out why it +crashed, the best thing to do is type run and let +your program run. After it crashes, you can type +where to find out where it crashed, or +info locals to see the values of all the local +variables. There's also a print that lets you look +at individual variables or what pointers point to. + +If your program is doing something unexpected, you can use the +break command to tell gdb to stop your program when it +gets to a specific function or line number: + +"break" in gdb + +(gdb) break my_function +(gdb) break 47 + + + +Now, when you type run your program will stop +at that "breakpoint" and you can use the other gdb commands to look at +the state of your program at that point, modify variables, and +step through your program's statements one at a +time. + +Note that you may specify additional arguments to the +run command to provide command-line arguments to +your program. These two cases are the same as far as your program is +concerned: + +Debugging with command line arguments + +bash$ myprog -t foo --queue 47 + +bash$ gdb myprog +(gdb) run -t foo --queue 47 + + + + + -- cgit v1.2.3