The "use BX" option is now a suggestion that BX be used if available. Use a macro to detect if BX is available at build time. If so, and the user requested it be used, then use it. Otherwise, error out. Macro courtesy Khem RAJ: http://lists.uclibc.org/pipermail/uclibc/2009-April/042301.html Signed-off-by: "Yann E. MORIN" Cc: Khem Raj Cc: Bernhard Reutner-Fischer Cc: Carmelo AMOROSO --- extra/Configs/Config.arm | 4 +++- libc/sysdeps/linux/arm/bits/arm_asm.h | 9 ++++++++- 2 files changed, 11 insertions(+), 2 deletions(-) --- a/extra/Configs/Config.arm +++ b/extra/Configs/Config.arm @@ -33,4 +33,6 @@ config COMPILE_IN_THUMB_MODE config USE_BX bool "Use BX in function return" help - Use BX instruction for THUMB aware architectures. + Say 'y' to use BX to return from functions on your thumb-aware + processor. Say 'y' if you need to use interworking. Say 'n' if not. + It is safe to say 'y' even if you're not doing interworking. --- a/libc/sysdeps/linux/arm/bits/arm_asm.h +++ b/libc/sysdeps/linux/arm/bits/arm_asm.h @@ -24,5 +24,12 @@ #define THUMB1_ONLY 1 #endif -#endif /* _ARM_ASM_H */ +#if defined(__USE_BX__) +# if ( defined (__ARM_ARCH_2__) || defined (__ARM_ARCH_3__) \ + || defined (__ARM_ARCH_3M__) || defined (__ARM_ARCH_4__) \ + ) +# error Use of BX was requested, but is not available on the target processor. +# endif /* ARCH level */ +#endif /* __USE_BX__ */ +#endif /* _ARM_ASM_H */