[lfs-support] questions about chapter 5.5.1

François Bissey francois.bissey at canterbury.ac.nz
Fri Mar 28 16:10:17 PDT 2014


On 28/03/2014, at 16:24, Bruce Dubbs <bruce.dubbs at gmail.com> wrote:

> François Bissey wrote:
>> Hi,
>> 
>> I suspect it may be a case of "to much knowledge is dangerous".
>> 
>> Having some experience
> 
> "some" experience is indeed a dangerous thing.
> 
> in building cross compilers and bootstrapping
>> systems in the past I found some elements in that chapter troubling
>> enough to stop and post here first:
>> 
>> 1) There are instructions to download and unpack gmp,mpfr and mpc.
>> But nowhere to configure && compile them.
>> The hints that I have from the remaining of your instructions is that
>> you don't want to install them.
> 
> They are built as a part of the gcc instructions in Chapter 5.  They are 
> built as separate libraries in Chapter 6.
> 
> "GCC now requires the GMP, MPFR and MPC packages. As these packages may 
> not be included in your host distribution, they will be built with GCC. 
> Unpack each package into the GCC source directory and rename the 
> resulting directories so the GCC build procedures will automatically use 
> them:”
> 

I never knew that gcc would do that, I have never seen it before in build instructions.
May be some spec files that I have seen for fedora may make more sense
if I revisited them.
May be it is because I am not a native english speaker but I didn’t understand that
this bit of text meant that gcc would build them by itself. If this is indeed the most frequently
asked question on the list I think it suggests the wording is unclear.

Just as an additional question: Is it a recent capacity or as it been present for a long
time?

>> 2) we are asked to gcc so that it looks for ld* in /tools/lib{,32,64} rather
>> than in plain /lib{,32,64}. Yet, at this stage we haven't built glibc
>> which would provide it, so there is nothing in /tools/lib* at this stage.
>> It looks to me like this will be useful in pass 2 but could lead to
>> breakage in pass 1.
> 
> Try it and see.  /tools/lib* is the first place it looks, but if not 
> found, it looks at the host's files.  That's why we build gcc twice.
> 

OK, I was not sure it would do that I was only expecting to do something like that
in stage 2. There are further questions that crowd my mind as a result but I’ll
keep for later when I have gone through the process and possibly done further experiments.

>> 3) configuration options for gmp and mpc? Only mpfr paths are given,
>> and they would need to be compiled first - statically I am guessing.
> 
> Just follow the instructions as they are written

Sure will, now that this is cleared


Francois


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