On 09/03/2010 09:56 AM, Tom Browder wrote:
I am trying to use m4 (version 1.4.13) to generate a C header file and
am approaching it cautiously because my experience with m4 has not
been comforting.
You may want to consider upgrading to 1.4.15, although I don't think
that will impact your usage issue.
My initial m4 input file has these lines:
=====>
divert(-1)
define(`hashdef', `#define')dnl
define(`Min', include(`conf/MINOR'))
divert(0)dnl
hashdef __PROGVER_MINOR__ Min
<====
When I execute "m4<m4 input file>" I get:
====>
#define __PROGVER_MINOR__ Min
<====
Notice 'Min is not expanded.
Is the '#' stopping it?
Correct. And that's because, by default, # is the m4 comment character,
and once hashdef is expanded, you have turned the rest of the line into
an m4 comment.
If so, how can I get the line I want.
By either disabling m4 comments:
changecom()
or by using proper quoting (so that hashdef no longer expands to a
comment character, but a quoted string that happens to contain #):
define(`hashdef', ``#'define')dnl
Also, to be robust to non-GNU m4, you should probably also double-quote
define, or use other tricks to ensure that you don't inadvertently end
up expanding the define built-in with zero arguments (GNU m4 explicitly
documents that the define built-in when invoked with zero arguments
expands to it's own name, as if it hadn't been a macro, but POSIX leaves
that bit unspecified):
define(`hashdef', ``#define'')dnl
--
Eric Blake [email protected] +1-801-349-2682
Libvirt virtualization library http://libvirt.org
