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From: | John Graham-Cumming |
Subject: | Re: need help with the Makefile |
Date: | Fri, 09 Sep 2005 13:47:31 +0200 |
User-agent: | Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.6) Gecko/20040208 Thunderbird/0.5 Mnenhy/0.6.0.104 |
address@hidden wrote:
a. should I ask user to pass some env variable such as KVER=2.4 or KVER=2.6 at the make command line and then check the $(KVER) and setup the flags accordingly.
Well that's one way to do it, if you can't do autodetection of the version that you are trying to build.
Also is it possible to check for empty variable and exist with some error msg like following check_ver: ifeq ($(strip $(KVER)),) @echo "Error: Please set KVER" Endif
That's not going to work because you've got a tab before ifeq and endif which means GNU Make is going to pass them to the shell and those are internal GNU Make preprocessor commands.
My recommendation is not to do the checking of KVER in a rule (because that rule might never get run). Instead just check KVER in the Makefile at the start and using $(error) to output the message.
ifeq ($(strip $(KVER)),) $(error Please set KVER before running Make) endif John. -- John Graham-Cumming address@hidden Home: http://www.jgc.org/ POPFile: http://getpopfile.org/ Sign up for my Spam and Anti-spam Newsletter at http://www.jgc.org/
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