Errors L6366E & L62242E

" Error: L6366E: uECC.o attributes are not compatible with the provided cpu and fpu attributes" indicates that the build attributes used in your lib built by the gcc compiler are different/incompatible with the ones currently used in your project.

You can use the fromelf.exe together with  --decode_build_attributes command line option to decode your lib file as well as your uECC.o to compare the attributes

https://www.keil.com/support/man/docs/armutil/armutil_pge1362128892751.htm

They must be aligned, otherwise you will get this error

So, this is what I get as output from executing 

fromelf.exe --decode_build_attributes libuECC.a

** Section #8 '.ARM.attributes' (SHT_ARM_ATTRIBUTES)
    Size   : 48 bytes

    'aeabi' file build attributes:
    0x000000:   05 41 52 4d 37 54 44 4d 49 00 06 02 08 01 09 01    .ARM7TDMI.......
    0x000010:   12 04 14 01 15 01 17 03 18 01 19 01 1a 01 1e 02    ................
        Tag_CPU_name = "ARM7TDMI"
        Tag_CPU_arch = ARM v4T (=2)
        Tag_ARM_ISA_use = ARM instructions were permitted to be used (=1)
        Tag_THUMB_ISA_use = Thumb instructions were permitted to be used (=1)
        Tag_ABI_PCS_wchar_t = Size of wchar_t is 4 (=4)
        Tag_ABI_FP_denormal = This code was permitted to require IEEE 754 denormal numbers (=1)
        Tag_ABI_FP_exceptions = This code was permitted to check the IEEE 754 inexact exception (=1)
        Tag_ABI_FP_number_model = This code may use all the IEEE 754-defined FP encodings (=3)
        Tag_ABI_align8_needed = Code was permitted to depend on the 8-byte alignment of 8-byte data items (=1)
        Tag_ABI_align8_preserved = Code was required to preserve 8-byte alignment of 8-byte data objects (=1)
        Tag_ABI_enum_size = Enum values occupy the smallest container big enough to hold all values (=1)
        Tag_ABI_optimization_goals = Optimized aggressively for speed, small size and debug illusion sacrificed (=2)

How do I see the attributes of my project and how would I align them?

Surely, the  messages are telling you which parts are in conflict:

Anvi said:

Build Attributes that are incompatible with the CPU attributes.
Tag_CPU_arch = ARM v4T (=2)
Tag_THUMB_ISA_use = Thumb instructions were permitted to be used (=1)
Tag_ARM_ISA_use = ARM instructions were permitted to be used (=1)

and

Anvi said:

attributes are incompatible with the image attributes.
... wchart-16 clashes with wchart-32.
... arm-isa clashes with m-profile.

For a start, it looks like your project is Cortex-M, but the library is ARM7TDMI ?

I see, thank you for your response. I'm trying to find documentation for the GNU ARM Embedded Toolchain on how to modify these attributes when compiling the library object. I can't seem to find anything explicit

I attempted to re-compile using my target cpu name: 

arm-none-eabi-gcc -Wall -O3 -mcpu=cortex-m3 -c uECC.c

error: target CPU does not support ARM mode

Anvi said:

and I get this error:

Well, you would: a Cortex-M3 indeed does not support ARM mode - it is Thumb only.

Anvi said:

how to modify these attributes when compiling the library object. I can't seem to find anything explicit

Did you read the 'Compilation Notes' in the documentation on the Github page you linked?

Have you tried contacting the author?

I see, I understand. I re-compiled using the following flags:

arm-none-eabi-gcc -Wall -O3 -fshort-wchar -mthumb -mcpu=cortex-m3 -mfix-cortex-m3-ldrd -c uECC.c 

I'm able to link the resulting object into my project now. Thanks for you guidance