[LFS Trac] #2648: GMP instructions (dev version) say to add ABI=32 to CFLAGS; should be separate variable

LFS Trac trac at linuxfromscratch.org
Mon May 3 08:10:22 PDT 2010

#2648: GMP instructions (dev version) say to add ABI=32 to CFLAGS; should be
separate variable
 Reporter:  drjones  |       Owner:  ken@…                   
     Type:  defect   |      Status:  new                     
 Priority:  normal   |   Milestone:  6.7                     
Component:  Book     |     Version:  SVN                     
 Severity:  normal   |    Keywords:  GMP                     

Comment(by ken@…):

 OK, I think I'm getting there.  The original part of this ticket only
 happens if CFLAGS are set.

 I'll categorise this second part as "building with wrong instructions".
 The host_cpu is picked up from config.sub, but can be overridden by
 --build.  Depending on what flavour of x86 cpu this is, different code is
 used to get the most from the cpu.

 If I read this correctly (line 4010 onwards, and 5046 onwards in
 5.0.1/configure), configure identifies the cpu and then builds code to
 suit it, irrespective of whether CFLAGS are passed or not.  Either we have
 a misidentified cpu (the c3 and suchlike used to cause problems in the
 past, but I would hope that they will be correctly identified by our
 temporary toolchain), or you have cases where you follow our instructions
 and hope to run on anything >= i486, but in this case a "common" build
 machine generates code for itself.

 If it's the latter, I don't think LFS gives guarantees about compatability
 across different machines.  The point is certainly worth noting, because
 some users will try this, but I think we can merely tell users in that
 situation to pass --build=[CPU]-linux to configure after choosing a value
 of [CPU] such as i486 from the x86 cpus listed under host_cpu in

Ticket URL: <http://wiki.linuxfromscratch.org/lfs/ticket/2648#comment:6>
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