Apple clang version 14.0.0 (clang-1400.0.17.3.1) fails the build
because stds.h defines `fallthrough` as a macro which is then
expanded when base.h evaluates
# if __has_attribute(fallthrough) && __clang_major__ >= 5
The macOS SDK defines `DISPATCH_FALLTHROUGH` as the macro instead
of `fallthrough`.
This change replaces the use of `fallthrough` in the tree with
`HEIM_FALLTHROUGH` and updates the declaration in configure logic
to define `HEIM_FALLTHROUGH` based upon existing definitions
(if any) of `fallthrough` or `DISPATCH_FALLTHROUGH`.
The pseudo keyword 'fallthrough' is defined such that case statement
blocks must end with any of these keywords:
* break;
* fallthrough;
* continue;
* goto <label>;
* return [expression];
*
* gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes
The macro is defined either as
__attribute__((__fallthrough__))
or as
do {} while (0) /* fallthrough */
not including the semicolon.
This change implements the Linux kernel style and updates several locations
where "/*fallthrough*/ and /* FALLTHROUGH */ were not previously replaced.
Externally imported code such as libedit, libtommath and sqlite are
restored to their unaltered state.
Change-Id: I69db8167b0d5884f55d96d72de3059a0235a1ba3
Although not required to address bad code generation in
some versions of gcc 9 and 10, a coding style that requires
explicit comparison of the result to zero before use is
both clearer and would have avoided the generation of bad
code.
This change converts all use of cmp function usage from
```
if (strcmp(a, b) || !strcmp(c, d)) ...
```
to
```
if (strcmp(a, b) != 0 || strcmp(c, d)) == 0
```
for all C library cmp functions and related:
- strcmp(), strncmp()
- strcasecmp(), strncasecmp()
- stricmp(), strnicmp()
- memcmp()
Change-Id: Ic60c15e1e3a07e4faaf10648eefe3adae2543188
