Re: Setting Variables depending on target being made

[John Graham-Cumming]

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Gary Hall wrote:
| cmp :
|         @ if [ ${dbg} = 0 ] ; then \
|                 MY_OPTS="${MY_OPT1} ${MY_OPT2}"; export MY_OPTS; \
|                 echo "Debug Off : dbg = ${dbg}"; \
|         else \
|             MY_OPTS="${MY_OPT1} ; \
|                 echo "Debug On : dbg = ${dbg}"; \
|         fi
|
|         echo "Options : ${OPTS}"; \


That's not going to work for two reasons:

1. You are setting MY_OPTS in the commands for cmp which does nothing to
change the value of MY_OPTS inside GNU Make: here you are just setting a
shell variable

2. Even if it did set MY_OPTS in the Makefile this still wouldn't work
because the commands for cmp would be run after all the other commands
in the Makefile (since cmp is the goal). You have the same problem with
the commands for cmp and cmpDbg which get run after the rest of the
build but attempt to output "Starting Compile...".

The right solution is to set MY_OPTS as a target-specific variable based
on the goal:

MY_OPT1 := +1
MY_OPT2 := -I/include -I/home/include

MY_OPTS := $(MY_OPT1)

cmp : compile

cmpDbg : MY_OPTS += $(MY_OPT2)
cmpDbg : compile

John.

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