Keep your current source file open in Xcode after a run completes (a.k.a don't die in main.m)

keep_current_file_open.sh

#! /bin/sh

# On alternate invocations, this script 
# saves the path of the source file currently open in Xcode
# and restores the file at that path in Xcode.
#
# By setting Xcode (in Behaviors) to run this script when "Run Starts" 
# and when "Run Completes", you can prevent it from switching to main.m 
# when a run finishes.
# See http://stackoverflow.com/questions/7682277/xcode-4-2-jumps-to-main-m-every-time-after-stopping-simulator 
# for a description of the problem and a bunch of solutions which don't work.

# We use the defaults system to save the source path.
# Change the domain to whatever you like.
DOMAIN="com.wearhere.keep_current_file_open"
KEY="savedSourcePath"


# The first time this script is invoked, this call will return a "does not exist" error.
# The second time this script it invoked, this call will return the saved source path.
# We copy stderr to stdout so that we can read both results using a single call.
savedSourcePath=`defaults read $DOMAIN $KEY 2>&1`

if [[ "$savedSourcePath" == *"does not exist"* ]]; then
	# read path of current source file out of Xcode
	sourcePath="`osascript << EOT
	tell application "Xcode"
		set windowName to (name of first window)
		set currentFileName to item 2 of (words of windowName)
		set currentSourceDocument to first item of (source documents whose name ends with currentFileName)
		set currentSourceFile to (file of currentSourceDocument)
		set currentSourcePath to (POSIX path of currentSourceFile)
	end tell
	return currentSourcePath
	EOT`"
	
	# save current source path
	defaults write $DOMAIN $KEY "$sourcePath"
else
	# open saved source path in Xcode
	open "$savedSourcePath"
	# clear saved source path
	defaults delete $DOMAIN $KEY
fi

For Xcode 4.2.1, at least, it seems that you can put ‘handle SIGKILL nostop noprint nopass’ into ~/.gdbinit (link). Even better!