Heap RAM was being allocated to print dicts and do some other types of
iterating. Now these iterations use 1 word of state on the stack.
Deleting elements from a dict was not allowing the value to be reclaimed
by the GC. This is now fixed.
sys.exit always raises SystemExit so doesn't need a special
implementation for each port. If C exit() is really needed, use the
standard os._exit function.
Also initialise mp_sys_path and mp_sys_argv in teensy port.
Eventually, viper wants to be able to use raw pointers to strings and
arrays for efficient access. But for now, let's just load strings as a
Python object so they can be used as normal. This will anyway be
compatible with eventual intended viper behaviour.
Addresses issue #857.
Type representing signed size doesn't have to be int, so use special value
which defaults to SSIZE_MAX, but as it's not defined by C standard (but rather
by POSIX), allow ports to set it.
Previously, mpz was restricted to using at most 15 bits in each digit,
where a digit was a uint16_t.
With this patch, mpz can use all 16 bits in the uint16_t (improvement
to mpn_div was required). This gives small inprovements in speed and
RAM usage. It also yields savings in ROM code size because all of the
digit masking operations become no-ops.
Also, mpz can now use a uint32_t as the digit type, and hence use 32
bits per digit. This will give decent improvements in mpz speed on
64-bit machines.
Test for big integer division added.
Code-info size, block name, source name, n_state and n_exc_stack now use
variable length encoded uints. This saves 7-9 bytes per bytecode
function for most functions.
This way, the native glue code is only compiled if native code is
enabled (which makes complete sense; thanks to Paul Sokolovsky for
the idea).
Should fix issue #834.
The heap allocation is now exactly as it was before the "faster gc
alloc" patch, but it's still nearly as fast. It is fixed by being
careful to always update the "last free block" pointer whenever the heap
changes (eg free or realloc).
Tested on all tests by enabling EXTENSIVE_HEAP_PROFILING in py/gc.c:
old and new allocator have exactly the same behaviour, just the new one
is much faster.
Recent speed up of GC allocation made the GC have a fragmented heap.
This patch restores "original fragmentation behaviour" whilst still
retaining relatively fast allocation. This patch works because there is
always going to be a single block allocated now and then, which advances
the gc_last_free_atb_index pointer often enough so that the whole heap
doesn't need scanning.
Should address issue #836.
With a file with 1 line (and an error on that line), used to show the
line as number 0. Now shows it correctly as line number 1.
But, when line numbers are disabled, it now prints line number 1 for any
line that has an error (instead of 0 as previously). This might end up
being confusing, but requires extra RAM and/or hack logic to make it
print something special in the case of no line numbers.
These functions are generally 1 machine instruction, and are used in
critical code, so makes sense to have them inline.
Also leave these functions uninverted (ie 0 means enable, 1 means
disable) and provide macro constants if you really need to distinguish
the states. This makes for smaller code as well (combined with
inlining).
Applied to teensy port as well.
Because (for Thumb) a function pointer has the LSB set, pointers to
dynamic functions in RAM (eg native, viper or asm functions) were not
being traced by the GC. This patch is a comprehensive fix for this.
Addresses issue #820.
This simple patch gives a very significant speed up for memory allocation
with the GC.
Eg, on PYBv1.0:
tests/basics/dict_del.py: 3.55 seconds -> 1.19 seconds
tests/misc/rge_sm.py: 15.3 seconds -> 2.48 seconds
Multiplication of a tuple, list, str or bytes now yields an empty
sequence (instead of crashing). Addresses issue #799
Also added ability to mult bytes on LHS by integer.
Can now index ranges with integers and slices, and reverse ranges
(although reversing is not very efficient).
Not sure how useful this stuff is, but gets us closer to having all of
Python's builtins.
reversed function now implemented, and works for tuple, list, str, bytes
and user objects with __len__ and __getitem__.
Renamed mp_builtin_len to mp_obj_len to make it publically available (eg
for reversed).
This happens for example for zero-size arrays. As .get_buffer() method now
has explicit return value, it's enough to distinguish success vs failure
of getting buffer.
This was a nasty bug to track down. It only had consequences when the
heap size was just the right size to expose the rounding error in the
calculation of the finaliser table size. And, a script had to allocate
a small (1 or 2 cell) object at the very end of the heap. And, this
object must not have a finaliser. And, the initial state of the heap
must have been all bits set to 1. All these conspire on the pyboard,
but only if your run the script fresh (so unused memory is all 1's),
and if your script allocates a lot of small objects (eg 2-char strings
that are not interned).
qstr_init is always called exactly before mp_init, so makes sense to
just have mp_init call it. Similarly with
mp_init_emergency_exception_buf. Doing this makes the ports simpler and
less error prone (ie they can no longer forget to call these).
Reduces by about a factor of 10 on average the amount of RAM needed to
store the line-number to bytecode map in the bytecode prelude.
Using CPython3.4's stdlib for statistics: previously, an average of
13 bytes were used per (bytecode offset, line-number offset) pair, and
now with this improvement, that's down to 1.3 bytes on average.
Large RAM usage before was due to some very large steps in line numbers,
both from the start of the first line in a function way down in the
file, and also functions that have big comments and/or big strings in
them (both cases were significant).
Although the savings are large on average for the CPython stdlib, it
won't have such a big effect for small scripts used in embedded
programming.
Addresses issue #648.
This removes mpz_as_int, since that was a terrible function (it
implemented saturating conversion).
Use mpz_as_int_checked and mpz_as_uint_checked. These now work
correctly (they previously had wrong overflow checking, eg
print(chr(10000000000000)) on 32-bit machine would incorrectly convert
this large number to a small int).
Many OSes/CPUs have affinity to put "user" data into lower half of address
space. Take advantage of that and remap such addresses into full small int
range (including negative part).
If address is from upper half, long int will be used. Previously, small
int was returned for lower quarter of address space, and upper quarter. For
2 middle quarters, long int was used, which is clearly worse schedule than
the above.
The user code should call micropython.alloc_emergency_exception_buf(size)
where size is the size of the buffer used to print the argument
passed to the exception.
With the test code from #732, and a call to
micropython.alloc_emergenncy_exception_buf(100) the following error is
now printed:
```python
>>> import heartbeat_irq
Uncaught exception in Timer(4) interrupt handler
Traceback (most recent call last):
File "0://heartbeat_irq.py", line 14, in heartbeat_cb
NameError: name 'led' is not defined
```
With unicode enabled, this patch allows reading a fixed number of
characters from text-mode streams; eg file.read(5) will read 5 unicode
chars, which can made of more than 5 bytes.
For an ASCII stream (ie no chars > 127) it only needs to do 1 read. If
there are lots of non-ASCII chars in a stream, then it needs multiple
reads of the underlying object.
Adds a new test for this case. Enables unicode support by default on
unix and stmhal ports.
dummy_data field is accessed as uint value (e.g.
in emit_write_bytecode_byte_ptr), but is not aligned as such, which causes
bus errors or incorrect behavior on any arch requiring strictly aligned
data (ARM pre-v7, MIPS, etc, etc).
Conflicts:
stmhal/pin_named_pins.c
stmhal/readline.c
Renamed HAL_H to MICROPY_HAL_H. Made stmhal/mphal.h which intends to
define the generic Micro Python HAL, which in stmhal sits above the ST
HAL.
Native emitter can now compile try/except blocks using nlr_push/nlr_pop.
It probably only works for 1 level of exception handling. It doesn't
work on Thumb (only x64).
Native emitter can also handle some additional op codes.
With this patch, 198 tests now pass using "-X emit=native" option to
micropython.
- rearrange/add definitions that were not there so it's easier to compare both
- use MICROPY_PY_SYS_PLATFORM in main.c since it's available anyway
- define EWOULDBLOCK, it is missing from ingw32
As stack checking is enabled by default, ports which don't call
stack_ctrl_init() are broken now (report RuntimeError on startup). Save
them trouble and just init stack control framework in interpreter init.
Squashed commit of the following:
commit 99dc21b67a895dc10d3c846bc158d27c839cee48
Author: Chris Angelico <rosuav@gmail.com>
Date: Thu Jun 12 02:18:54 2014 +1000
Optimize as per TODO (thanks Damien!)
commit 5bf0153ecad8348443058d449d74504fc458fe51
Author: Chris Angelico <rosuav@gmail.com>
Date: Tue Jun 10 08:42:06 2014 +1000
Test a default (= UTF-8) encode and decode
commit c962057ac340832c4fde60896f656a3fe3ad78a9
Merge: e2c9782 195de32
Author: Chris Angelico <rosuav@gmail.com>
Date: Tue Jun 10 05:23:03 2014 +1000
Merge branch 'master' into unicode, resolving conflict on py/obj.h
commit e2c9782a65eb57f481d441d40161de427e1940ba
Author: Chris Angelico <rosuav@gmail.com>
Date: Tue Jun 10 05:05:57 2014 +1000
More whitespace fixups
commit 086a2a0f57afbc1f731697fd5d3a0cbbb80e5418
Author: Chris Angelico <rosuav@gmail.com>
Date: Tue Jun 10 05:04:20 2014 +1000
Properly implement string slicing
commit 0d339a143e2b6442366145e7f3d64aada293eaa0
Author: Chris Angelico <rosuav@gmail.com>
Date: Tue Jun 10 02:24:11 2014 +1000
Support slicing in str_index_to_ptr, and fix a bounds error
commit 24371c7267d360e77cf5eabc2e8ce9a73d2ee0da
Author: Chris Angelico <rosuav@gmail.com>
Date: Tue Jun 10 02:10:22 2014 +1000
Break out index-to-pointer calculation into a function
commit 616c24ac014c3ca56008428c506034dd1bfff7a8
Author: Chris Angelico <rosuav@gmail.com>
Date: Tue Jun 10 02:03:11 2014 +1000
Add tests of string slicing, which currently fail
commit a24d19f676fe8cc21dad512d91b826892e162a5b
Author: Chris Angelico <rosuav@gmail.com>
Date: Tue Jun 10 01:56:53 2014 +1000
Change string indexing to not precalculate the charlen, and add test for neg indexing
commit 0bcc7ab89eafb2ae53195e94c9bea42a4e886b64
Author: Chris Angelico <rosuav@gmail.com>
Date: Sun Jun 8 22:09:17 2014 +1000
Clean up constant qstr declarations now that charlen isn't needed
commit 5473e1a1dba2124b7b0c207f2964293cfbe80167
Author: Chris Angelico <rosuav@gmail.com>
Date: Sun Jun 8 07:18:42 2014 +1000
Remove the charlen field from strings, calculating it when required
commit 5c1658ec71aefbdc88c261ce2e57dc7670cdc6ef
Author: Chris Angelico <rosuav@gmail.com>
Date: Sun Jun 8 07:11:27 2014 +1000
Get rid of mp_obj_str_get_data_len() which was used in only one place
commit a019ba968b4e8daf7f3674f63c5cc400e304c509
Author: Chris Angelico <rosuav@gmail.com>
Date: Sun Jun 8 06:58:26 2014 +1000
Add a unichar_charlen() function to calculate length-in-characters from length-in-bytes
commit 44b0d5cff846ba487c526ed95be1b3d1cd3d762a
Author: Chris Angelico <rosuav@gmail.com>
Date: Sun Jun 8 06:32:44 2014 +1000
Use utf8_get/next_char in building up a string's repr
commit 30d1bad33f7af90f1971987c39864c8fcf3f5c21
Author: Chris Angelico <rosuav@gmail.com>
Date: Sun Jun 8 06:10:45 2014 +1000
Make utf8_get_char() and utf8_next_char() actually do what their names say
commit bc990dad9afb8ec112f5e7f7f79d5ab415da0e72
Author: Chris Angelico <rosuav@gmail.com>
Date: Sun Jun 8 02:10:59 2014 +1000
Revert "Add PEP 393-flags to strings and stub usage."
This reverts commit c239f509521d1a0f9563bf9c5de0c4fb9a6a33ba.
commit f9bebb28ad52467f2f2d7a752bb033296b6c2f9b
Author: Chris Angelico <rosuav@gmail.com>
Date: Sat Jun 7 15:41:48 2014 +1000
Whitespace fixes
commit 279de0c8eb3cb186914799ccc5ee94ea97f56de4
Author: Chris Angelico <rosuav@gmail.com>
Date: Sat Jun 7 15:28:35 2014 +1000
Formatting/layout improvements - introduce macros for UTF-8 byte detection, add braces. No functional changes.
commit f1911f53d56da809c97b07245f5728a419e8fb30
Author: Chris Angelico <rosuav@gmail.com>
Date: Sat Jun 7 11:56:02 2014 +1000
Make chr() Unicode-aware
commit f51ad737b48ac04c161197a4012821d50885c4c7
Author: Chris Angelico <rosuav@gmail.com>
Date: Sat Jun 7 11:44:07 2014 +1000
Make a string's repr Unicode-aware
commit 01bd68684611585d437982dccdf05b33cbedc630
Author: Chris Angelico <rosuav@gmail.com>
Date: Sat Jun 7 11:33:43 2014 +1000
Expand the Unicode tests
commit 7bc91904f899f8012089fc14a06495680a51e590
Author: Chris Angelico <rosuav@gmail.com>
Date: Sat Jun 7 11:27:30 2014 +1000
Record byte lengths for byte strings
commit bb132120717cf176dcfb26f87fa309378f76ab5f
Author: Chris Angelico <rosuav@gmail.com>
Date: Sat Jun 7 11:25:06 2014 +1000
Make ord() Unicode-aware
commit 03f0cbe9051b62192be97b59f84f63f9216668bf
Author: Chris Angelico <rosuav@gmail.com>
Date: Sat Jun 7 10:24:35 2014 +1000
Retain characters as UTF-8 encoded Unicode
commit e924659b85c001916a5ff7f4d1d8b3ebe2bf0c2f
Author: Chris Angelico <rosuav@gmail.com>
Date: Sat Jun 7 08:37:27 2014 +1000
Add support for \u and \U escapes, but not \N (with explanatory comment)
commit 231031ac5f0346e4ffcf9c4abec2bd33f566232c
Author: Chris Angelico <rosuav@gmail.com>
Date: Sat Jun 7 05:09:35 2014 +1000
Add character length to qstr
commit 6df1b946fb17d8d5df3d91b21cde627c3d4556a8
Author: Chris Angelico <rosuav@gmail.com>
Date: Fri Jun 6 13:48:36 2014 +1000
Add test of UTF-8 encoded source file resulting in properly formed string
commit 16429b81a8483cf25865ed11afd81a7d9c253c26
Author: Chris Angelico <rosuav@gmail.com>
Date: Fri Jun 6 13:44:15 2014 +1000
Make len(s) return character length (even though creation's still buggy)
commit cd2cf6663cc47831dbc97819ad5c50ad33f939d3
Author: Chris Angelico <rosuav@gmail.com>
Date: Fri Jun 6 13:15:36 2014 +1000
HACK - When indexing a qstr, count its charlen. Stupidly inefficient but POC.
All tests pass now, though string creation is still buggy.
commit 47c234584d3358dfa6b4003d5e7264105d17b8f7
Author: Chris Angelico <rosuav@gmail.com>
Date: Fri Jun 6 13:15:32 2014 +1000
objstr: Record character length separately from byte length
CAUTION: Buggy, may crash stuff - qstr needs equivalent functionality too
commit b0f41c72af27d3b361027146025877b3d7e8785c
Author: Chris Angelico <rosuav@gmail.com>
Date: Fri Jun 6 05:37:36 2014 +1000
Beginnings of UTF-8 support - construct strings from that many UTF-8-encoded chars, and subscript bytes the same way
commit 89452be641674601e9bfce86dc71c17c3140a6cf
Author: Chris Angelico <rosuav@gmail.com>
Date: Fri Jun 6 05:28:47 2014 +1000
Update comments - now aiming for UTF-8 rather than PEP 393 strings
commit c239f509521d1a0f9563bf9c5de0c4fb9a6a33ba
Author: Chris Angelico <rosuav@gmail.com>
Date: Wed Jun 4 05:28:12 2014 +1000
Add PEP 393-flags to strings and stub usage.
The test suite all passes, but nothing has actually been changed.
Such mechanism is important to get stable Python functioning, because Python
function calling is handled with C stack. The idea is to sprinkle
STACK_CHECK() calls in places where there can be C recursion.
TODO: Add more STACK_CHECK()'s.
Expected to be set on command line, with the idea being that for different
targets, there're different smartass ABIs which strive to put unneeded
sections into executables, etc., so let people have flexible way to
strip that.
The option name is similar to previously introduced CLFAGS_EXTRA &
LDFLAGS_EXTRA.
char can be signedness, and using signedness types is dangerous - it can
lead to negative offsets when doing table lookups. We apparently should just
ban char usage.
This will allow roughly the same behavior as Python3 for non-ASCII strings,
for example, print("<phrase in non-Latin script>".split()) will print list
of words, not weird hex dump (like Python2 behaves). (Of course, that it
will print list of words, if there're "words" in that phrase at all, separated
by ASCII-compatible whitespace; that surely won't apply to every human
language in existence).
Functionality we provide in builtin io module is fairly minimal. Some
code, including CPython stdlib, depends on more functionality. So, there's
a choice to either implement it in C, or move it _io, and let implement other
functionality in Python. 2nd choice is pursued. This setup matches CPython
too (_io is builtin, io is Python-level).
Benefits: won't crash baremetal targets, will provide Python source location
when not implemented feature used (it will no longer provide C source
location, but just grep for error message).
there are special tweaks and paths to be considered. Just provide some
defaults, in case the values are undefined.
- py-version.sh does not need any bash specific features.
- Use libdl only on Linux for now. FreeBSD provides dl*() calls from libc.
Some small fixed:
- Combine 'x' and 'X' cases in str format code.
- Remove trailing spaces from some lines.
- Make exception messages consistently begin with lower case (then
needed to change those in objarray and objtuple so the same
constant string data could be used).
- Fix bug with exception message having %c instead of %%c.
Add keyword args to dict.update(), and ability to take a dictionary as
argument.
dict() class constructor can now use dict.update() directly.
This patch loses fast path for dict(other_dict), but is that really
needed? Any anyway, this idiom will now re-hash the dictionary, so is
arguably more memory efficient.
Addresses issue #647.
This may seem a bit of a risky change, in that it may introduce crazy
bugs with respect to volatile variables in the VM loop. But, I think it
should be fine: code_state points to some external memory, so the
compiler should always read/write to that memory when accessing the
ip/sp variables (ie not put them in registers).
Anyway, it passes all tests and improves on all efficiency fronts: about
2-4% faster (64-bit unix), 16 bytes less stack space per call (64-bit
unix) and slightly less executable size (unix and stmhal).
The reason it's more efficient is save_ip and save_sp were volatile
variables, so were anyway stored on the stack (in memory, not regs).
Thus converting them to code_state->{ip, sp} doesn't cost an extra
memory dereference (except maybe to get code_state, but that can be put
in a register and then made more efficient for other uses of it).
Conflicts:
py/vm.c
Fixed stack underflow check. Use UINT_FMT/INT_FMT where necessary.
Specify maximum VM-stack byte size by multiple of machine word size, so
that on 64 bit machines it has same functionality as 32 bit.
This improves stack usage in callers to mp_execute_bytecode2, and is step
forward towards unifying execution interface for function and generators
(which is important because generators don't even support full forms
of arguments passing (keywords, etc.)).
Needed to pop the iterator object when breaking out of a for loop. Need
also to be careful to unwind exception handler before popping iterator.
Addresses issue #635.
This helps the compiler do its optimisation, makes it clear which
variables are local per opcode and which global, and makes it consistent
when extra variables are needed in an opcode (in addition to old obj1,
obj2 pair, for example).
Could also make unum local, but that's for another time.
This completes non-automatic interning of strings in the parser, so that
doc strings don't take up RAM. It complicates the parser and compiler,
and bloats stmhal by about 300 bytes. It's complicated because now
there are 2 kinds of parse-nodes that can be strings: interned leaves
and non-interned structs.
io.FileIO is binary I/O, ans actually optional. Default file type is
io.TextIOWrapper, which provides str results. CPython3 explicitly describes
io.TextIOWrapper as buffered I/O, but we don't have buffering support yet
anyway.
Now schedule is: for native types, we call ->make_new() C-level method, which
should perform actions of __new__ and __init__ (note that this is not
compliant, but is efficient), but for user types, __new__ and __init__ are
called as expected.
Also, make sure we convert scalar attribute value to a bound-pair tight in
mp_obj_class_lookup() method, which avoids converting it again and again in
its callers.
__debug__ now resolves to True or False. Its value needs to be set by
mp_set_debug().
TODO: call mp_set_debug in unix/ port.
TODO: optimise away "if False:" statements in compiler.
Updated functions now do proper checking that n_kw==0, and are simpler
because they don't have to explicitly raise an exception. Down side is
that the error messages no longer include the function name, but that's
acceptable.
Saves order 300 text bytes on x64 and ARM.
This is not fully correct re: error handling, because we should check that
that types are used consistently (only str's or only bytes), but magically
makes lot of functions support bytes.
Two things are handled here: allow to compare native subtypes of tuple,
e.g. namedtuple (TODO: should compare type too, currently compared
duck-typedly by content). Secondly, allow user sunclasses of tuples
(and its subtypes) be compared either. "Magic" I did previously in
objtype.c covers only one argument (lhs is many), so we're in trouble
when lhs is native type - there's no other option besides handling
rhs in special manner. Fortunately, this patch outlines approach with
fast path for native types.
This was hit when trying to make urlparse.py from stdlib run. Took
quite some time to debug.
TODO: Reconsile bound method creation process better, maybe callable is
to generic type to bind at all?
Parser shouldn't raise exceptions, so needs to check when memory
allocation fails. This patch does that for the initial set up of the
parser state.
Also, we now put the parser object on the stack. It's small enough to
go there instead of on the heap.
This partially addresses issue #558.
"object" type in MicroPython currently doesn't implement any methods, and
hopefully, we'll try to stay like that for as long as possible. Even if we
have to add something eventually, look up from there might be handled in
adhoc manner, as last resort (that's not compliant with Python3 MRO, but
we're already non-compliant). Hence: 1) no need to spend type trying to
lookup anything in object; 2) no need to allocate subobject when explicitly
inheriting from object; 3) and having multiple bases inheriting from object
is not a case of incompatible multiple inheritance.
This patch simplifies the glue between native emitter and runtime,
and handles viper code like inline assember: return values are
converted to Python objects.
Fixes issue #531.
You can now do:
X = const(123)
Y = const(456 + X)
and the compiler will replace X and Y with their values.
See discussion in issue #266 and issue #573.
In case of empty non-blocking read()/write(), both return None. read()
cannot return 0, as that means EOF, so returns another value, and then
write() just follows. This is still pretty unexpected, and typical
"if not len:" check would treat this as EOF. Well, non-blocking files
require special handling!
This also kind of makes it depending on POSIX, but well, anything else
should emulate POSIX anyway ;-).
Need to have a policy as to how far we go adding keyword support to
built ins. It's nice to have, and gets better CPython compatibility,
but hurts the micro nature of uPy.
Addresses issue #577.
There are 2 locations in parser, and 1 in compiler, where memory
allocation is not precise. In the parser it's the rule stack and result
stack, in the compiler it's the array for the identifiers in the current
scope. All other mallocs are exact (ie they don't allocate more than is
needed).
This patch adds tuning options (MP_ALLOC_*) to mpconfig.h for these 3
inexact allocations.
The inexact allocations in the parser should actually be close to
logarithmic: you need an exponentially larger script (absent pathological
cases) to use up more room on the rule and result stacks. As such, the
default allocation policy for these is now to start with a modest sized
stack, but grow only in small increments.
For the identifier arrays in the compiler, these now start out quite
small (4 entries, since most functions don't have that many ids), and
grow incrementally by 6 (since if you have more ids than 4, you probably
have quite a few more, but it wouldn't be exponentially more).
Partially addresses issue #560.
This will work if MICROPY_DEBUG_PRINTERS is defined, which is only for
unix/windows ports. This makes it convenient to user uPy normally, but
easily get bytecode dump on the spot if needed, without constant recompiles
back and forth.
TODO: Add more useful debug output, adjust verbosity level on which
specifically bytecode dump happens.
Blanket wide to all .c and .h files. Some files originating from ST are
difficult to deal with (license wise) so it was left out of those.
Also merged modpyb.h, modos.h, modstm.h and modtime.h in stmhal/.
By default mingw outputs 3 digits instead of the standard 2 so all float
tests using printf fail. Using setenv at the start of the program fixes this.
To accomodate calling platform specific initialization a
MICROPY_MAIN_INIT_FUNC macro is used which is called in mp_init()
The original parsing would error out on any C declarations that are not typedefs
or extern variables. This limits what can go in mpconfig.h and mpconfigport.h,
as they are included in qstr.h. For instance even a function declaration would be
rejected and including system headers is a complete no-go.
That seems too limiting for a global config header, so makeqstrdata now
ignores everything that does not match a qstr definition.
alloca() is declared in alloca.h which als happens to be included by stdlib.h.
On mingw however it resides in malloc.h only.
So if we include alloca.h directly, and add an alloca.h for mingw in it's port
directory we can get rid of the mingw-specific define to include malloc.h
and the other ports are happy as well.
