Public bug reported:
The multilib setup is not working in the bionic version of gcc-arm-none-
eabi (gcc v6.3.1). For example, if I build a project with
"-mcpu=cortex-m4" or "-march=armv7e-m" and link with:
arm-none-eabi-gcc -o someoutput.elf object1.o object2.o -mthumb -Wl
,--gc-sections -ffast-math -march=armv7-m -Tlinker_script.ld
I get as output:
/usr/lib/gcc/arm-none-eabi/6.3.1/../../../arm-none-eabi/bin/ld: error:
/usr/lib/gcc/arm-none-eabi/6.3.1/../../../arm-none-eabi/lib/crt0.o: Conflicting
CPU architectures 13/1
/usr/lib/gcc/arm-none-eabi/6.3.1/../../../arm-none-eabi/bin/ld: failed to merge
target specific data of file
/usr/lib/gcc/arm-none-eabi/6.3.1/../../../arm-none-eabi/lib/crt0.o
arm-none-eabi-readelf -A on any of my object files produces:
Attribute Section: aeabi
File Attributes
Tag_CPU_name: "Cortex-M4"
Tag_CPU_arch: v7E-M
Tag_CPU_arch_profile: Microcontroller
Tag_THUMB_ISA_use: Thumb-2
Tag_ABI_PCS_wchar_t: 4
Tag_ABI_FP_number_model: Finite
Tag_ABI_align_needed: 8-byte
Tag_ABI_align_preserved: 8-byte, except leaf SP
Tag_ABI_enum_size: small
Tag_ABI_optimization_goals: Prefer Speed
Tag_CPU_unaligned_access: v6
But "arm-none-eabi-readelf -A /usr/lib/gcc/arm-none-eabi/6.3.1
/../../../arm-none-eabi/lib/crt0.o" gives
Attribute Section: aeabi
File Attributes
Tag_CPU_arch: v4
Tag_ARM_ISA_use: Yes
If I define "void _init(void){}" and use -nostartfiles, compilation
finishes but the resulting binary does not work. I have not examined the
output file but it appears that it has somehow linked to code containing
ARM as well as thumb code:
# readelf -A someoutput.elf
Attribute Section: aeabi
File Attributes
Tag_CPU_name: "Cortex-M4"
Tag_CPU_arch: v7E-M
Tag_CPU_arch_profile: Microcontroller
Tag_ARM_ISA_use: Yes
Tag_THUMB_ISA_use: Thumb-2
Tag_ABI_PCS_wchar_t: 4
Tag_ABI_FP_denormal: Needed
Tag_ABI_FP_exceptions: Needed
Tag_ABI_FP_number_model: IEEE 754
Tag_ABI_align_needed: 8-byte
Tag_ABI_align_preserved: 8-byte, except leaf SP
Tag_ABI_enum_size: small
Tag_ABI_optimization_goals: Prefer Speed
Tag_CPU_unaligned_access: v6
I can work around the problem by manually specifying compatible versions
of libc and libgcc with -nostdlib:
-nostdlib /usr/lib/arm-none-eabi/newlib/thumb/libc.a /usr/lib/gcc/arm-
none-eabi/6.3.1/thumb/v7e-m/libgcc.a
This produces a working binary. However, there is still something wrong
because readelf -A still includes "Tag_ARM_ISA_use: Yes":
Attribute Section: aeabi
File Attributes
Tag_CPU_name: "Cortex-M4"
Tag_CPU_arch: v7E-M
Tag_CPU_arch_profile: Microcontroller
Tag_ARM_ISA_use: Yes
Tag_THUMB_ISA_use: Thumb-2
Tag_ABI_PCS_wchar_t: 4
Tag_ABI_FP_denormal: Needed
Tag_ABI_FP_exceptions: Needed
Tag_ABI_FP_number_model: IEEE 754
Tag_ABI_align_needed: 8-byte
Tag_ABI_align_preserved: 8-byte, except leaf SP
Tag_ABI_enum_size: small
Tag_ABI_optimization_goals: Prefer Speed
Tag_CPU_unaligned_access: v6
Previously, using xenial and gcc v4, readelf gives the following output on the
output binary:
Attribute Section: aeabi
File Attributes
Tag_CPU_name: "7E-M"
Tag_CPU_arch: v7E-M
Tag_CPU_arch_profile: Microcontroller
Tag_THUMB_ISA_use: Thumb-2
Tag_ABI_PCS_wchar_t: 4
Tag_ABI_FP_denormal: Needed
Tag_ABI_FP_exceptions: Needed
Tag_ABI_FP_number_model: IEEE 754
Tag_ABI_align_needed: 8-byte
Tag_ABI_enum_size: small
Tag_ABI_optimization_goals: Prefer Speed
Tag_CPU_unaligned_access: v6
(Also, what happened to gdb-arm-none-eabi?)
** Affects: gcc-arm-none-eabi (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1767223
Title:
multilib selects wrong start files
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