Arm C Compiler doesn't support gmtime()

[simonbutcher]

Description

• Type: Bug
• Priority: Major

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Bug

OS
Mbed OS

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The Arm C Compiler does not support gmtime() as stated in the documentation. Yet, Mbed TLS will build with it, but calls to gmtime() will return a NULL - therefore MBEDTLS_HAVE_TIME can't work with ARM C Compiler.

We probably need a check in check_config.h to detect the ARM C Compiler and to issue an error if MBEDTLS_HAVE_TIME is enabled.

[ciarmcom]

ARM Internal Ref: IOTSSL-2486

[simonbutcher]

If a compiler or platform (such as the Arm C Compiler) doesn't provide gmtime() or gmtime_r(), we now allow users integrating the library to provide their own implementation of either by implementing the function mbedtls_platform_gmtime_r() which is an abstraction of gmtime_r(). This feature was introduced in PR #1927.

Therefore it doesn't matter if gmtime() isn't supported on any given platform - but it is however the responsibility of those integrating Mbed TLS with the platform to provide their own implementation.

And to be clear - the Mbed TLS project has no plans to provide it's own implementation of gmtime() or gmtime_r().

Therefore this issue can now be closed.