Checking The Gcc Version In A Makefile?

Answer :

I wouldn't say its easy, but you can use the shell function of GNU make to execute a shell command like gcc --version and then use the ifeq conditional expression to check the version number and set your CFLAGS variable appropriately.

Here's a quick example makefile:

CC = gcc GCCVERSION = $(shell gcc --version | grep ^gcc | sed 's/^.* //g') CFLAGS = -g  ifeq "$(GCCVERSION)" "4.4.3"     CFLAGS += -Wtype-limits endif  all:         $(CC) $(CFLAGS) prog.c -o prog 

Edit: There is no ifgt. However, you can use the shell expr command to do a greater than comparison. Here's an example

CC = gcc GCCVERSIONGTEQ4 := $(shell expr `gcc -dumpversion | cut -f1 -d.` \>= 4) CFLAGS = -g  ifeq "$(GCCVERSIONGTEQ4)" "1"     CFLAGS += -Wtype-limits endif  all:         $(CC) $(CFLAGS) prog.c -o prog 

To transform full 3-part gcc version (not only first digit) into numerical format, suitable for comparison (e.g. 40701) use

gcc -dumpversion | sed -e 's/\.\([0-9][0-9]\)/\1/g' -e 's/\.\([0-9]\)/0\1/g' -e 's/^[0-9]\{3,4\}$/&00/' 

Which addresses the possibility of double-digit numbers in any of the version part, and possibility of missing 3-rd part of the version in output of gcc -dumpversion (which is the case in some earlier gcc versions).

So to test the version in makefile, use something like (note $$ inside last sed command)

GCC_GTEQ_472 := $(shell expr `gcc -dumpversion | sed -e 's/\.\([0-9][0-9]\)/\1/g' -e 's/\.\([0-9]\)/0\1/g' -e 's/^[0-9]\{3,4\}$$/&00/'` \>= 40702) ifeq "$(GCC_GTEQ_472)" "1"   ... endif 

I just encountered this problem where I needed to test the first two digits of gcc and wanted a more readable option than the clever sed hackery above. I used bc to do the comparison since it supports floating point (expr treats non-integers as strings):

GCC_VER_GTE44 := $(shell echo `gcc -dumpversion | cut -f1-2 -d.` \>= 4.4 | bc ) ifeq ($(GCC_VER_GTE44),1) ... endif 

If they release gcc 4.10 after gcc 4.9, then a bit of sed hacking is necessary, but this is still pretty readable:

GCC_VER_GTE44 := $(shell echo `gcc -dumpversion | cut -f1-2 -d.` \>= 4.4 | sed -e 's/\./*100+/g' | bc ) ifeq ($(GCC_VER_GTE44),1) ... endif