[Bug libgcc/60464] [arm] ARM -mthumb version of libgcc contains ARM (non-thumb) code; not safe for thumb-only architectures

[Bug libgcc/60464] [arm] ARM -mthumb version of libgcc contains ARM (non-thumb) code; not safe for thumb-only architectures

[jeremygccb at baymoo dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60464

--- Comment #1 from Jeremy Cooper <jeremygccb at baymoo dot org> ---
Seeing as this could be an assembler bug, my arm-none-eabi-as is:

$ arm-none-eabi-as -v
GNU assembler version 2.23.2 (arm-none-eabi) using BFD version (GNU Binutils)
2.23.2

[Bug libgcc/60464] [arm] ARM -mthumb version of libgcc contains ARM (non-thumb) code; not safe for thumb-only architectures

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60464

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |INVALID
           Severity|critical                    |normal

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
>Configuring and building gcc 4.8.2 for the target 'arm-none-eabi' results in a thumb version of libgcc.a that is not entirely suitable for thumb-only processors

That is correct.  The default is to configure arm target to be armv5 processor.
 You need to configure for building for armv6m or an armv7m (or even armv7-a)
if you want to use -mthumb for a thumb (or thumb2 only) processor.

[Bug libgcc/60464] [arm] ARM -mthumb version of libgcc contains ARM (non-thumb) code; not safe for thumb-only architectures

[jeremygccb at baymoo dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60464

Jeremy Cooper <jeremygccb at baymoo dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |UNCONFIRMED
         Resolution|INVALID                     |---

--- Comment #3 from Jeremy Cooper <jeremygccb at baymoo dot org> ---
I have done as you suggested and built gcc for the target "armv7m-none-eabi"
and the "thumb" version of libgcc.a still has functions with ARM code. Shall I
re-open this bug or create a new one?

[Bug libgcc/60464] [arm] ARM -mthumb version of libgcc contains ARM (non-thumb) code; not safe for thumb-only architectures

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60464

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Can you configure with --with-arch=armv7-m and try again?  You might need to
edit config/arm/t-arm-elf to enable only the multi-lib that you need.

>armv7m-none-eabi

Does nothing really to change the default target.

[Bug libgcc/60464] [arm] ARM -mthumb version of libgcc contains ARM (non-thumb) code; not safe for thumb-only architectures

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60464

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |INVALID

--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Invalid as explained before.  arm*-eabi says it is for armv5 rather than armv6
with thumb and thumb2.

[Bug libgcc/60464] [arm] ARM -mthumb version of libgcc contains ARM (non-thumb) code; not safe for thumb-only architectures

[jeremygccb at baymoo dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60464

--- Comment #6 from Jeremy Cooper <jeremygccb at baymoo dot org> ---
(In reply to Andrew Pinski from comment #4)
> Can you configure with --with-arch=armv7-m and try again?  You might need to
> edit config/arm/t-arm-elf to enable only the multi-lib that you need.

I am sorry if I appear dense, but which multi-lib would I need? Recall that I'm
trying to target a cortex-m3, so what exactly do I need for the multi-lib
options in t-arm-elf? (And once this is done, how can I effect this change with
a configure option, rather than having to edit GCC source?)

MULTILIB_OPTIONS     = ?
MULTILIB_DIRNAMES    = ?
MULTILIB_EXCEPTIONS  = ?
MULTILIB_MATCHES     = ?

[Bug libgcc/60464] [arm] ARM -mthumb version of libgcc contains ARM (non-thumb) code; not safe for thumb-only architectures

[jeremygccb at baymoo dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60464

--- Comment #7 from Jeremy Cooper <jeremygccb at baymoo dot org> ---
I have managed to resolve the problem by doing two things. However, one of them
is still distasteful (editing the GCC 4.8.2 source).

1. Edited gcc/config/arm/t-arm-elf, uncommenting the following lines:

MULTILIB_OPTIONS      += march=armv7
MULTILIB_DIRNAMES     += thumb2
MULTILIB_EXCEPTIONS   += march=armv7* marm/*march=armv7*
MULTILIB_MATCHES      += march?armv7=march?armv7-a
MULTILIB_MATCHES      += march?armv7=march?armv7-r
MULTILIB_MATCHES      += march?armv7=march?armv7-m
MULTILIB_MATCHES      += march?armv7=mcpu?cortex-a8
MULTILIB_MATCHES      += march?armv7=mcpu?cortex-r4
MULTILIB_MATCHES      += march?armv7=mcpu?cortex-m3

2. configure --target=arm-none-eabi --enable-languages=c --disable-libssp
--disable-libstdcxx

Is there a reason these were commented out? Is the armv7 multilib unstable?

[Bug libgcc/60464] [arm] ARM -mthumb version of libgcc contains ARM (non-thumb) code; not safe for thumb-only architectures

[rearnsha at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60464

--- Comment #8 from Richard Earnshaw <rearnsha at gcc dot gnu.org> ---
(In reply to Jeremy Cooper from comment #7)

> Is there a reason these were commented out? Is the armv7 multilib unstable?

Volume of variants that have to be compiled at build time.  Each enabled entry
practically doubles the build time for the libraries.