missing limits.h in bignum.c

[krisk0]

Summary

File library/bignum.c is using CHAR_BIT macro but does not include limits.h.

The file does not compile when other included headers do not include limits.h, for instance on Linux/glibc/gcc 10.3.0.

System information

Mbed TLS version (number or commit id): 3c28fd3
Operating system and version: Gentoo Linux x86_64, glibc
Configuration (if not default, please attach mbedtls_config.h):
Compiler and options (if you used a pre-built binary, please indicate how you obtained it): -O2 -march=native
Additional environment information:

Expected behavior

everything compiles

Actual behavior

library/bignum.c does not compile

Steps to reproduce

Attempt to build with gcc 10.3.0 on Glibc'ish Linux with MBEDTLS_BIGNUM_C is enabled

Additional information

I suggest that you add #include <limits.h> to bignum.c.

[gilles-peskine-arm]

How are you building the library exactly? In Mbed TLS 3.0 there's an inclusion chain bignum.c → common.h → mbedtls/build_info.h → mbedtls/check_config.h → limits.h. This is quite convoluted and it would be a good idea for bignum.c to include limits.h directly, but I can't see how you could end up building bignum.c without including limits.h.

This is a genuine bug in 2.16 and 2.2x where the inclusion of check_config.h is recommended, but since it goes through the user's config.h, it isn't guaranteed.

[krisk0]

Yes, my config.h did not include check_config.h. Does it need to? If yes then this is my fault.

[gilles-peskine-arm]

With Mbed TLS 3.0.0+, there shouldn't be a way to bypass check_config.h. If you managed to do it, that's a bug of its own, please let us know how.

With Mbed TLS 2.x, it is possible to bypass check_config.h. The fact that the library doesn't build when config.h just contains #include MBEDTLS_BIGNUM_C and nothing else is a bug.

[krisk0]

I experimented with an old version (2.20, commit 1146b4e), but mentioned fresh commit 3c28fd3 in my bug report. Sorry for that.
If check_config.h is included by config.h, then bignum compiles.
I don't mind if you close the bug.