Added support for Apple Silicon (M1).

[emeryberger]

Describe your changes
The existing compiler flags did not allow builds on Apple Silicon platforms (e.g., the M1 mini). This PR rectifies this situation, adding __arm64 detection and ensuring it is treated as a 64-bit platform.

Testing performed
Run with a test that uses the BDE library.

[osubboo]

Noted. We'll look into it.

[AlisdairM]

These lines need properly indenting to match surrounding #if blocks

[AlisdairM]

Wordwrap with a line continuation for exceeding 79 columns

[notadragon]

We shouldn't reference system macros directly but should be checking for the proper BSLS_PLATFORM macros.

Please change this (and the other preprocessor check below) to this:

#if    !(defined(BSLS_PLATFORM_OS_SOLARIS))                                   \
    && !(defined(BSLS_PLATFORM_OS_AIX))                                       \
    && !(defined(BSLS_PLATFORM_OS_DARWIN) && defined(BSLS_PLATFORM_CPU_ARM))

[AlisdairM]

Wordwrap with a line continuation for exceeding 79 columns

[notadragon]

Please change the macro guards in bsls_spinlock as I specified and then verify that this still builds on your M1. If it does we can get this PR landed.

Thanks.

[notadragon]

We shouldn't reference system macros directly but should be checking for the proper BSLS_PLATFORM macros.

Please change this (and the other preprocessor check below) to this:

#if    !(defined(BSLS_PLATFORM_OS_SOLARIS))                                   \
    && !(defined(BSLS_PLATFORM_OS_AIX))                                       \
    && !(defined(BSLS_PLATFORM_OS_DARWIN) && defined(BSLS_PLATFORM_CPU_ARM))

[mversche]

Should this PR be closed in preference to #275?

[emeryberger]

That does look like a more comprehensive PR than this one (I was just about to test).

[emeryberger]

I updated to a more recent BDE and it no longer builds on the M1. I can work on it but if the other PR already works for a more recent version of BDE, it'd make more sense to merge that one. Let me know.