Incorrect indentation in some multiline conditional compilation directives

[gilles-peskine-arm]

The tool we use for code styling (uncrustify) has a bug that causes it to use misleading indentation in continuation lines for conditional compilation directives. For example:

#if defined(MBEDTLS_SSL_HANDSHAKE_WITH_CERT_ENABLED) && \
    (defined(MBEDTLS_SSL_RENEGOTIATION)              || \
    defined(MBEDTLS_SSL_VARIABLE_BUFFER_LENGTH))

We'd like defined(MBEDTLS_SSL_VARIABLE_BUFFER_LENGTH) to be left-aligned with defined(MBEDTLS_SSL_RENEGOTIATION) so that it's obvious to the reader that this is 1 && (2 || 3) and not (1 && 2) || 3. But that's not what we get from uncrustify.

This is just a code readability issue — it doesn't affect the behavior of the code, unless of course someone who edited it was mislead by the presentation.

You can use the following one-big-liner to look for problematic lines (many of them exhibit an instance of the bug):

perl -ne '/^ *# *(el)?if\b.*\\$/ or next; $_ .= <> while /\\$/; $x = $_; $x =~ tr/()\n//dc; 1 while $x =~ s/\(\)//g; $x =~ s/\n+\Z$//; print "\e[35m$ARGV:$.:\e[0m\n$_" if $x } continue { close ARGV if eof' $(git ls-files '**.c' '**.h' '**.function' ':!**/check_config.h')

This issue exists so that we can remember the readability issue if it comes up again in code reviews, and as a repository for any investigation we do towards a solution. Definition of done: we find a way to no longer have this misleading indentation, either by upgrading uncrustify if the bug gets fixed, or by tweaking the configuration if we find a workaround.