CODEWITHSUNDEEP
c++autotoolsautoconfautomakem4
Ivan Dives
Ivan Dives

Reputation: 517

How to tell AC_SUBST to not substitute variables in arguments?

I'm using autotools to build my project and I'd like to globally set AM_CPPFLAGS to -I$(top_srcdir)/include.

https://stackoverflow.com/a/325436/2592351 this answer helped me and I'm doing the "include $(top_srcdir)/include" hack and it works.

However I'd like to do the "AC_SUBST" way described there as it looks cleaner. The problem is when I add this to my configure.ac:

AC_SUBST([AM_CPPFLAGS], [-I$(top_srcdir)/include])

then $(top_srcdir) is expanded too soon and I get AM_CPPFLAGS = -I/include in subdir/Makefile{,.in}.

And I don't get how to escape it. 

-I@top_srcdir@/include
-I\$(top_srcdir)/include
-I$$(top_srcdir)/include

all these failed for various reasons.

Please help. How should I write the AC_SUBST so $(top_srcdir) is not escaped before it gets to Makefile{,.in}? Or maybe I should use something other than AC_SUBST?

Upvotes: 3

Views: 1660

Answers (1)

Diego Elio Pettenò
Diego Elio Pettenò

Reputation: 3240

Don't set AM_CPPFLAGS in your configure.ac. If you find yourself repeating the same preamble in multiple Makefile.am you should be using non-recursive automake.

But in this particular case, you should get away with it if you do

AM_CPPFLAGS='-I$(top_srcdir)/include'
AC_SUBST([AM_CPPFLAGS])

Because then the string is set quoted in the bash variable, and afterward expanded as a literal. Using AC_SUBST to set it up, it gets quoted by "" which then causes $(top_srcdir) to be shell-expanded.

Upvotes: 1

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