From 6cb6ef73152475df27298f4189d6a7e512491d81 Mon Sep 17 00:00:00 2001 From: Christopher Faylor Date: Sat, 13 Jul 2002 21:13:37 +0000 Subject: [PATCH] cleanup a tad --- winsup/cygwin/how-to-debug-cygwin.txt | 26 ++++++++++++++++++-------- 1 file changed, 18 insertions(+), 8 deletions(-) diff --git a/winsup/cygwin/how-to-debug-cygwin.txt b/winsup/cygwin/how-to-debug-cygwin.txt index 100e9ac34..2549565bf 100644 --- a/winsup/cygwin/how-to-debug-cygwin.txt +++ b/winsup/cygwin/how-to-debug-cygwin.txt @@ -1,4 +1,4 @@ -Copyright 2001 Red Hat Inc., Egor Duda +Copyright 2001, 2002 Red Hat Inc., Egor Duda So, your favorite program has crashed? And did you say something about 'stackdump'? Or it just prints its output from left to right and @@ -9,14 +9,17 @@ you can do something better than that. You can debug the problem yourself, and even if you can't fix it, your analysis may be very helpful. Here's the (incomplete) howto on cygwin debugging. -1. The first thing you'll need to do is to build cygwin1.dll and your +1. First things first + + The first thing you'll need to do is to build cygwin1.dll and your crashed application from sources. To debug them you'll need debug information, which is normally stripped from executables. You probably also want to build a version of the dll with more debugging capabilities by reconfiguring your build directory, specifying the --enable-debugging option to configure. -2. Create known-working cygwin debugging environment. +2. Creating a known-working cygwin debugging environment + - create a separate directory, say, c:\cygdeb, and put known-working cygwin1.dll and gdb.exe in it. - create a wrapper c:\cygdeb\debug_wrapper.cmd: @@ -28,13 +31,15 @@ set CYGWIN_TESTING=1 c:\cygdeb\gdb.exe -nw %1 %2 =================================== -3. Try to use cygwin's JIT debugging facility: +3. Using cygwin's JIT debugging facility + add 'error_start=c:\cygdeb\debug_wrapper.cmd' to CYGWIN environment variable. When some application encounters critical error, cygwin will stop it and execute debug_wrapper.cmd, which will run gdb and make it to attach to the crashed application. -4. Strace. +4. Strace + You can run your program under 'strace' utility, described if user's manual. If you know where the problem approximately is, you can add a bunch of additional debug_printf()s in the source code and see what they print in @@ -49,7 +54,8 @@ c:\cygdeb\gdb.exe -nw %1 %2 starts does not inherit a cygwin environment. It is equivalent to starting a program from the command prompt. -5. Problems at early startup. +5. Problems at early startup + Sometimes, something crashes at the very early stages of application initialization, when JIT debugging facility is not yet active. Ok, there's another environment variable that may help. Create program_wrapper.cmd: @@ -71,6 +77,8 @@ c:\some\path\bad_program.exe some parameters After that you can normally step through the code in cygwin1.dll and bad_program.exe +6. More problems at early startup + You can also set a CYGWIN_DEBUG variable to force the debugger to pop up only when a certain program is run: @@ -84,7 +92,8 @@ set CYGWIN_DEBUG=cat.exe=gdb.exe Note that it bears repeating that both of the above options are *only* available when configuring cygwin with --enable-debugging. -6. Heap corruption. +7. Heap corruption + If your program crashes at malloc() or free() or when it references some malloc()'ed memory, it looks like heap corruption. You can configure and build special version of cygwin1.dll which includes heap sanity checking. @@ -92,7 +101,8 @@ set CYGWIN_DEBUG=cat.exe=gdb.exe however, that this version of dll is _very_ slow (10-100 times slower than normal), so use it only when absolutely necessary. -7. Program dies when running under strace. +8. Program dies when running under strace + If your program crashes when you run it using strace but runs ok (or has a different problem) otherwise, then there may be a problem in one of the strace *_printf statements. Usually this is caused by a change in arguments -- 2.43.5