An increment to Jon Turney's stackdump2backtrace script

[Mark Geisert]

For those Cygwin developers who tend to attract stackdump files...

..mark (who defines an alias 'bt' to launch the script because he can't get gdb 
out of his head)

h/t to JT
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#!/bin/bash
#
#	stackdump2backtrace (incremented)
#	Munges a Cygwin stackdump file into a real backtrace
#
#	Based on nifty stackdump2backtrace script by Jon Turney, as
#	posted in https://sourceware.org/ml/cygwin/2015-08/msg00311.html
#
#	2018/10/01 increment by Mark A. Geisert

# The user provides the name of the stackdump file
STACKDUMP=$1
if [ -z "$STACKDUMP" ]; then
    echo Usage: $0 name-of-stackdump-file
    exit 1
fi
if [ ! -e "$STACKDUMP" ]; then
    echo cannot find stackdump file $STACKDUMP
    exit 1
fi

# Look for executable's best available stashed debug info
IMG1=/usr/lib/debug/usr/bin/${STACKDUMP%.stackdump}.dbg

# If no stashed debug info available for executable, read from EXE
if [ ! -e "$IMG1" ]; then
    IMG1=${STACKDUMP%.stackdump}

    # If we can't find the EXE, try to locate it with 'which'
    if [ ! -e "$IMG1" ]; then
	IMG1=`basename $IMG1`
	IMG1=`which $IMG1`
    fi
fi

# If no luck locating executable image file, bail
if [ ! -e "$IMG1" ]; then
    echo cannot find executable file $IMG1
    exit 1
fi

# Look for Cygwin DLL's best available stashed debug info
IMG2=/usr/lib/debug/usr/bin/cygwin1.dbg
if [ ! -e "$IMG2" ]; then
    IMG2="" # not found; just use what ldd locates later on
fi

# Construct list of image files to resolve addresses against
# Sorting into reverse order seems to improve address lookup performance
OTHERS=`ldd $IMG1 | awk '{print $3}' | sort -r | tr '\\n' ' '`
IMAGES="$IMG1 $IMG2 $OTHERS"

display() {
    declare -g IMAGES

    # look up address $1 in each known image; break on first success
    for img in $IMAGES
    do
	line=`addr2line -asfiC -e $img $1`
	echo $line | fgrep -q "??:0"
	if [ $? -ne 0 ]; then
	    break
	fi
    done

    # state machine for prettier display of addr2line output
    addr=""
    temp=""
    for word in $line
    do
	case $word in
	0x*)
	    addr=$word
	    temp=""
	    ;;
	\?\?:0 | *.*:*)
	    echo "$addr | $word | $temp"
	    addr="     or maybe     "
	    temp=""
	    ;;
	*)
	    temp+="$word "
	    ;;
	esac
    done
}

# Read and process each stack frame line of the stackdump file
grep "^Exception:" $STACKDUMP
awk '/^[0-9A-F][0-9A-F]/ {print $2}' $STACKDUMP | while read ADDR
do
    display $ADDR
done | column -o' ' -t -s'|'

# Deal with register-dump form of stackdump file. No frames here.
COUNT=`grep -c "^[0-9A-F][0-9A-F]" $STACKDUMP`
if [ X"$COUNT" = X0 ]; then
    ADDR=`grep "^Exception:" $STACKDUMP | awk '{print $4}' | sed 's/rip=/0x/'`
    if [ X"$ADDR" != X ]; then
	display $ADDR | column -o' ' -t -s'|'
    fi
    echo no stack frames present
fi

# And that's all the misinfotainment we have time for
exit 0
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