This change is made for two reasons:
1. A 3rd-party library (eg berkeley-db-1.xx, axtls) may use the system
provided errno for certain errors, and yet MicroPython stream objects
that it calls will be using the internal mp_stream_errno. So if the
library returns an error it is not known whether the corresponding errno
code is stored in the system errno or mp_stream_errno. Using the system
errno in all cases (eg in the mp_stream_posix_XXX wrappers) fixes this
ambiguity.
2. For systems that have threading the system-provided errno should always
be used because the errno value is thread-local.
For systems that do not have an errno, the new lib/embed/__errno.c file is
provided.
This commit removes the Makefile-level MICROPY_FATFS config and moves the
MICROPY_VFS_FAT config to the Makefile level to replace it. It also moves
the include of the oofatfs source files in the build from each port to a
central place in extmod/extmod.mk.
For a port to enabled VFS FAT support it should now set MICROPY_VFS_FAT=1
at the level of the Makefile. This will include the relevant oofatfs files
in the build and set MICROPY_VFS_FAT=1 at the C (preprocessor) level.
Setting MICROPY_PY_USSL and MICROPY_SSL_MBEDTLS at the Makefile-level will
now build mbedTLS from source and include it in the build, with the ussl
module using this TLS library. Extra settings like MBEDTLS_CONFIG_FILE may
need to be provided by a given port.
If a port wants to use its own mbedTLS library then it should not set
MICROPY_SSL_MBEDTLS at the Makefile-level but rather set it at the C level,
and provide the library as part of the build in its own way (see eg esp32
port).
Damien George