make_notes.txt

Print variable in Makefile to stdout:
$(info $$var is [${var}])


GNU Make symbol shortcuts (automatic variables):
http://www.gnu.org/software/make/manual/html_node/Automatic-Variables.html
$@ The file name of the target of the rule.
$< The name of the first prerequisite.
$^ The names of all the prerequisites.


Special symbols in reciple lines:
http://stackoverflow.com/questions/3477292/what-do-and-do-as-prefixes-to-recipe-lines-in-make
@ suppresses the normal 'echo' of the command that is executed.
- means ignore the exit status of the command that is executed (normally, a non-zero exit status would stop that part of the build).
+ means 'execute this command under make -n' (when commands are not normally executed).


Variable assignment types:
http://stackoverflow.com/questions/448910/makefile-variable-assignment
VARIABLE = value  => (Lazy Set) Normal setting of a variable - values within it are recursively expanded when the variable is used, not when it's declared
VARIABLE := value => (Immediate Set) Setting of a variable with simple expansion of the values inside - values within it are expanded at declaration time.
VARIABLE ?= value => (Set If Absent) Setting of a variable only if it doesn't have a value
VARIABLE += value => (Append) Appending the supplied value to the existing value (or setting to that value if the variable didn't exist)


Preprocessor defined macros:
http://sourceforge.net/p/predef/wiki/Home/
http://fortranwiki.org/fortran/show/Predefined+preprocessor+macros


Get preprocessor definitions manually:
http://stackoverflow.com/questions/9349754/generate-list-of-preprocessor-macros-defined-by-the-compiler/
gcc -E -dM - < /dev/null
icc -E -dM - < /dev/null
gfortran -cpp -E -dM empty.f
ifort -E -fpp /dev/null -dryrun 2>&1 | grep -e -D | cut -c 5-