[CMake] how to compile single source file with debug options?

[Sergey Spiridonov]

Hi all

On 10/06/16 14:05, Sergey Spiridonov wrote:

> To debug and fix our applications/libraries we often need to recompile
> single source file in a debug mode. With the our current build system it
> is as simple, as touching a file an starting make with debug option. It
> will then recompile that single file with -O0 -g and with -DDEBUG and
> relink target application/library.

I implemented following solution (proposed by Elizabeth A. Fischer
elizabeth.fischer at columbia.edu):

1. Create a wrapper script ggcc/gg++ around the gcc/g++. It checks if
env variable PDL has "d" and if true, then removes release options and
inserts debug options instead.

2. The very first time cmake must be started like "CC=ggcc CXX=gg++
cmake" (it is not enough just to rerun cmake, you must clean everything
first)

3. To recompile some of the source files in debug mode, one has to touch
them and run "make PDL=d"

Here is the wrapper script (inspired by [1])

[1] https://github.com/gawen947/gcc-wrapper/

#!/bin/bash
# This is a wrapper around gcc compiler to allow switching to debug mode
"on the fly"
# you can enable debugging by executing "make PDL=d"
#
#
# (may be also trigger debug mode by creating empty sourcefile.cc.debug
in the same directory?)

# TODO: pass this from cmake(CMakeList.txt)->make
GAM_DEBUG_FLAGS="-Og -g -DGAM_DEBUG -ggdb -fno-inline -fno-default-inline"
GAM_REMOVE_DEBUG_FLAGS="-O3 -finline-functions -fexpensive-optimizations"

# what is cheaper, call external program or use bash instead of sh?

newcmd=""
if [ ${0##*/} == "ggcc" ]; then
  TOOL="gcc"
elif [ ${0##*/} == "gg++" ]; then
  TOOL="g++"
else
  echo "wrapper for gcc or g++"
  exit 120
fi


if [[ "$PDL" == *"d"* ]]; then
  # add GAM_DEBUG_FLAGS, remove GAM_REMOVE_DEBUG_FLAGS

  INSERTED=0
  for arg in $*; do
    if [ "-O3" == "$arg" ]; then
      INSERTED=1
      newcmd="$newcmd $GAM_DEBUG_FLAGS"
      continue
    fi
    # note spaces around env variables, they are essential
    if [[ " $GAM_DEBUG_FLAGS $GAM_REMOVE_FLAGS " == *" $arg "* ]]; then
      continue
    fi
    newcmd="$newcmd $arg"
  done
  if [ "$INSERTED" == 1 ]; then
      echo $TOOL $newcmd
      exec $TOOL $newcmd
  else
      exec $TOOL "$@"
  fi
else
  exec $TOOL "$@"
fi


Hope this can be useful for somebody else...
-- 
Best regards, Sergey Spiridonov