Subject: Re: [PATCH 3/6] Facilitate debugging Git executables in tests with gdb

From: Jonathan Nieder <[email-masked]>
Date: Fri, 30 Oct 2015 12:02:56 -0700

Junio C Hamano wrote:
> Johannes Schindelin <[email-masked]> writes:
>> On Tue, 27 Oct 2015, Junio C Hamano wrote:

>>> It can be called GDB=1, perhaps?
>>
>> No, this is way too generic. As I only test that the environment
>> variable's existence, even something like GDB=/usr/opt/gdb/bin/gdb would
>> trigger it.
>>
>> I could be talked into GDB_GIT=1, though.
>
> As I said in another message, I have no preference myself over the
> name of this variable (or making it a shell function like Duy
> mentioned, which incidentally may give us more visual pleasantness
> by losing '=').
>
> I'd just be happy as long as the feature becomes available, and I'd
> leave the choice of consistent and convenient naming to others who
> have stronger opinions ;-)

Here's a suggested patch.

-- >8 --
From: Johannes Schindelin <[email-masked]>
Subject: Facilitate debugging Git executables in tests with gdb

When prefixing a Git call in the test suite with 'debug ', it will now
be run with GDB, allowing the developer to debug test failures more
conveniently.

Signed-off-by: Johannes Schindelin <[email-masked]>
Signed-off-by: Jonathan Nieder <[email-masked]>
---
 t/README                | 5 +++++
 t/test-lib-functions.sh | 8 ++++++++
 wrap-for-bin.sh         | 8 +++++++-
 3 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/t/README b/t/README
index 35438bc..1dc908e 100644
--- a/t/README
+++ b/t/README
@@ -563,6 +563,11 @@ library for your script to use.
    argument.  This is primarily meant for use during the
    development of a new test script.
 
+ - debug <git-command>
+
+   Run a git command inside a debugger. This is primarily meant for
+   use when debugging a failing test script.
+
  - test_done
 
    Your test script must have test_done at the end.  Its purpose
diff --git a/t/test-lib-functions.sh b/t/test-lib-functions.sh
index 6dffb8b..73e37a1 100644
--- a/t/test-lib-functions.sh
+++ b/t/test-lib-functions.sh
@@ -145,6 +145,14 @@ test_pause () {
 	fi
 }
 
+# Wrap git in gdb. Adding this to a command can make it easier to
+# understand what is going on in a failing test.
+#
+# Example: "debug git checkout master".
+debug () {
+	 GIT_TEST_GDB=1 "$@"
+}
+
 # Call test_commit with the arguments "<message> [<file> [<contents> [<tag>]]]"
 #
 # This will commit a file with the given contents and the given commit
diff --git a/wrap-for-bin.sh b/wrap-for-bin.sh
index 701d233..db0ec6a 100644
--- a/wrap-for-bin.sh
+++ b/wrap-for-bin.sh
@@ -19,4 +19,10 @@ GIT_TEXTDOMAINDIR='@@BUILD_DIR@@/po/build/locale'
 PATH='@@BUILD_DIR@@/bin-wrappers:'"$PATH"
 export GIT_EXEC_PATH GITPERLLIB PATH GIT_TEXTDOMAINDIR
 
-exec "${GIT_EXEC_PATH}/@@PROG@@" "$@"
+if test -n "$GIT_TEST_GDB"
+then
+	unset GIT_TEST_GDB
+	exec gdb --args "${GIT_EXEC_PATH}/@@PROG@@" "$@"
+else
+	exec "${GIT_EXEC_PATH}/@@PROG@@" "$@"
+fi
-- 
2.6.0.rc2.230.g3dd15c0