Re: [PATCH] arm: do not abort EABI check for bootstrapping

[Joseph Myers <joseph at codesourcery dot com>]

On Thu, 20 Nov 2014, Mike Frysinger wrote:

> The change to simplify the EABI/OABI check from a tuple to a compile test
> broke the ability to bootstrap a cross-compiler when generating the glibc
> headers.  At that point, there is no compiler yet, so this compile-time
> test will always fail.  Wrap the error with a basic sanity check so that
> if the compiler fails, we assume this setup.

I don't see a reason to treat this test any differently from many other 
configure tests - we expect a working compiler, but may or may not fail 
configure if the breakage is such that no compiler >= GCC 4.6 should fail 
the test (in such cases, we don't actually need to have configure tests).

The ideal bootstrap procedure we're aiming for is as described at 
<https://sourceware.org/ml/libc-alpha/2012-03/msg00960.html>.  We don't 
quite have it, but only in that GCC needs reconfiguring and rebuilding for 
step 5: a basic GCC with static-only libgcc (configured in a way that 
causes inhibit_libc to be defined) can build glibc, and the resulting 
glibc is identical to one built after an alternating series of bootstrap 
GCC and glibc builds, but you need to reconfigure at toplevel to get a GCC 
that can build and use shared libgcc and other libraries.  (And also a 
glibc build tree built with static-only libgcc may not be able to run the 
testsuite properly; certainly you need a C++-capable compiler to run some 
tests.)

Nothing in this desired procedure involves configuring glibc without 
having a compiler for the relevant system.

> Note: an alternative might be to just delete the EABI check altogether.
> It's not like an OABI compiler will be able to properly build glibc ...

If we don't think it's realistic for someone to attempt building with an 
OABI compiler and get confused by the failure later in the build, that's a 
possibility.

(If anything, failing for non-ARM compilers is a feature - it seems quite 
plausible for someone to attempt building glibc for a different system 
without realising they first need to build a cross compiler, or with their 
configuration wrong in some way so that the cross compiler isn't used.)

-- 
Joseph S. Myers
joseph@codesourcery.com