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The project that I am trying to build has default flags 

CFLAGS = -Wall -g -O2

CXXFLAGS = -g -O2

I need to append a flag -w to both these variables (to remove: 'consider all warnings as errors')

I have a method to work it out, give

make 'CFLAGS=-Wall -g -O2 -w'; 'CXXFLAGS=-g -O2 -w'

OR

Run ./configure and statically modify Makefile

But I want to append my options with the existing options while running configure or make

The post Where to add a CFLAG, such as -std=gnu99, into an autotools project conveniently uses a macro to achieve this.

BenMorel
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Vigneshwaren
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1 Answers1

74

You almost have it right; why did you add the semicolon?

To do it on the configure line:

 ./configure CFLAGS='-g -O2 -w' CXXFLAGS='-g -O2 -w'

To do it on the make line:

 make CFLAGS='-g -O2 -w' CXXFLAGS='-g -O2 -w'

However, that doesn't really remove consider all warnings as errors; that removes all warnings. So specifying both -Wall and -w doesn't make sense. If you want to keep the warnings but not have them considered errors, use the -Wall -Wno-error flags.

Alternatively, most configure scripts which enable -Werror by default also have a flag such as --disable-werror or similar. Run ./configure --help and see if there's something like that.

MadScientist
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    Is there a way for me to NOT specify this statitcally evertime, like, CFLAGS=' $CFLAGS ', to retain whatever is already configured and without knowing it as well. – Vigneshwaren May 01 '14 at 12:40
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    No, that's not possible (at least not without modifying the makefile). According to the autoconf coding standards the default value of `CFLAGS` is always only enabling debugging/optimization, so it should normally always be `-g -O2` for most systems. It's not correct (according to the coding standards) to add other important flags such as `-I`, `-D`, etc. into `CFLAGS`. So it should be safe to always just override it. – MadScientist May 01 '14 at 15:08
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    If you cannot assign CFLAGS without retaining the package defaults, then the software packaging contains a bug which should be reported to the package maintainer. – William Pursell May 21 '14 at 14:12