musl: use a more specific fix for ARM thumb + frame pointers
PATCH v2 1/1 musl: use a more specific fix for ARM thumb + frame pointers
When compiling for Thumb or Thumb2, frame pointers _must_ be disabled since the Thumb frame pointer in r7 clashes with musl's use of inline asm to make syscalls (where r7 is used for the syscall NR).
In most cases, frame pointers will be disabled automatically due to the optimisation level, but appending an explicit -fomit-frame-pointer to CFLAGS handles cases where optimisation is set to -O0 or frame pointers have been enabled by -fno-omit-frame-pointer earlier in CFLAGS, etc.
Note that this limitation applies both to gcc and clang, the only difference between the two being that where gcc aborts with an error about reusing r7, clang apparently silently generates broken code:
https://bugs.llvm.org/show_bug.cgi?id=34165
--- meta/recipes-core/musl/musl_git.bb | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)
meta/recipes-core/musl/musl_git.bb +7 -1
@@ -28,7 +28,13 @@ export CROSS_COMPILE="${TARGET_PREFIX}" LDFLAGS += "-Wl,-soname,libc.so" -ARM_INSTRUCTION_SET_toolchain-clang = "arm" +# When compiling for Thumb or Thumb2, frame pointers _must_ be disabled since the +# Thumb frame pointer in r7 clashes with musl's use of inline asm to make syscalls +# (where r7 is used for the syscall NR). In most cases, frame pointers will be +# disabled automatically due to the optimisation level, but append an explicit +# -fomit-frame-pointer to handle cases where optimisation is set to -O0 or frame +# pointers have been enabled by -fno-omit-frame-pointer earlier in CFLAGS, etc. +CFLAGS_append_arm = " ${@bb.utils.contains('TUNE_CCARGS', '-mthumb', '-fomit-frame-pointer', '', d)}" CONFIGUREOPTS = " \ --prefix=${prefix} \
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1.9.1