This uses the existing mechanism for statically compiled C libraries,
to allow the user to export their own C libraries in a similar way.
User exported libraries can be added on top of statically compiled C
libraries or exist on their own (by setting SEXP_USE_STATIC_LIBS_EMPTY).
This is lighter-weight than building a full index->cursor table for
the string, adding a constant two words to the memory required to
store a string, as opposed to one word for every n characters. The
cached cursor is used for any string-ref operation requesting an index
after the most-recently-requested index, making potentially quadratic
repeated string-ref procedures run in linear time. In theory, it could
also use a heuristic to speed up moving backwards through the string
when it thinks that moving the old cursor backwards would be faster
than starting again at the start of the string. In practice, my
logging of when the cached cursor is actually reused during the Chibi
compilation and startup process shows that the most common case of
moving backwards is going back to the start of the string anyway.
Benchmarks to follow.
Replace explicit recursion by heap allocations
in sexp_mark_one code.
This prevents crashes caused by stack overflow.
In particular, fixes issue #601.
As an optimization, allocate a fixed sized stack buffer first,
which should be enough for "normal" uses.
When that stack overflows, switch to heap.
Also, store "ranges" on the stack, instead of the actual sexp's,
using the fact that sexp's of a single parent are continous in memory.
This patch doesn't remove recursion on the context saves
because it didn't seem like they overflow in practice.
But changing that is simple having the stack interface.
Under Unix with SEXP_64_BIT defined, sexp_sint_t is defined as 'long'.
But we would get the equivalent format specifier SEXP_PRIdFIXNUM from
the OS-defined PRId64 in <inttypes.h>. MacOS defines it as "lld". This
causes the clang printf checker to emit a warning about the 'long' and
'long long' mismatch.
Fix by avoiding system-defined PRId32 and PRId64 format specifiers and
always defining SEXP_PRIdFIXNUM as "d", "ld" or "lld" according to our
definition of sexp_sint_t as int, long or long long. This also means
we don't need to include <inttypes.h> any more.
