bignum: excessively long string literal triggers clang precautionary warning

[aaronmdjones]

When compiling bignum.c with clang, I receive the following warning:

mbedtls/library/bignum.c:1125:9: warning: string literal of length 4872 exceeds maximum length 4095 that ISO C99 compilers are required to support [-Woverlength-strings]
        MULADDC_INIT
        ^~~~~~~~~~~~
mbedtls/include/mbedtls/bn_mul.h:165:9: note: expanded from macro 'MULADDC_INIT'
        "movq   %3, %%rsi           \n\t"   \
        ^

It seems as if removing the trailing spaces before \n\t might be a good approach to reduce its length while not removing any instructions.

[ciarmcom]

ARM Internal Ref: IOTSSL-772

[simonbutcher]

Thanks for the feedback. Can I ask what version of clang you are using? I haven't seen these warnings so far. I'm sure it's a legitimate issue, but I'd like to ensure I can reproduce it and make it part of our test regime before we fix it.

[aaronmdjones]

 $ clang -g -O2 -DMBEDTLS_CONFIG_FILE='"mbedtls-cfg.h"' -Isrc/include -Imbedtls/include \
   -Wall -Wextra -Wpedantic -D_FORTIFY_SOURCE=2 -fstack-protector-strong -fPIC -DPIC \
   -Wa,--noexecstack -c -o mbedtls/library/bignum.o mbedtls/library/bignum.c

mbedtls/library/bignum.c:1125:9: warning: string literal of length 4872 exceeds maximum
                                          length 4095 that ISO C99 compilers are required
                                          to support [-Woverlength-strings]
        MULADDC_INIT
        ^~~~~~~~~~~~

mbedtls/include/mbedtls/bn_mul.h:165:9: note: expanded from macro 'MULADDC_INIT'
        "movq   %3, %%rsi           \n\t"   \
        ^

1 warning generated.

 $ clang --version
Debian clang version 3.5.0-10 (tags/RELEASE_350/final) (based on LLVM 3.5.0)
Target: x86_64-pc-linux-gnu
Thread model: posix