RE: nested backticks in Makefile

["Dave Korn" <dave dot korn at artimi dot com>]

On 27 March 2007 17:55, DJ Delorie wrote:

> When cross compiling with a sysroot, you sometimes end up with nested
> backticks. 
> 
> The case we're seeing it with is m32r-elf, where gcc_tooldir is defined
> thusly: 
> 
> gcc_tooldir = $(libsubdir)/$(unlibsubdir)/`echo $(exec_prefix) | sed -e
> 's|^$(prefix)||' -e 's|/$(dollar)||' -e 's|^[^/]|/|' -e
> 's|/[^/]*|../|g'`$(target_noncanonical)  
> 
> and SYSTEM_HEADER_DIR is thusly:
> 
> CROSS_SYSTEM_HEADER_DIR = $(gcc_tooldir)/sys-include
> SYSTEM_HEADER_DIR = `echo $(CROSS_SYSTEM_HEADER_DIR) | sed -e :a -e
> 's,[^/]*/\.\.\/,,' -e ta` 
> 
> Note that we have gcc_tooldir inside backticks, resulting in
> `...`...`...`, which bash obviously is going to misinterpret.
> 
> Given that we require GNU make, is the right solution to use $(shell
> echo ...)  for one of those to disambiguate it?

  Or how about using ':=' to force immediate evaluation?  Does $gcc_tooldir
change during the course of a build?  If not, it seems pointlessly wasteful to
repeatedly invoke shell/echo/sed every single time it's referred to...

    cheers,
      DaveK
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