As far as I can tell, these are not checked for the sake of efficiency.
This silences compiler diagnostics when building CircuitPython
```
../../extmod/ulab/code/approx.c:25:12: error: no previous prototype for ‘approx_python_call’ [-Werror=missing-prototypes]
mp_float_t approx_python_call(const mp_obj_type_t *type, mp_obj_t fun, mp_float_t x, mp_obj_t *fargs, uint8_t nparams) {
^~~~~~~~~~~~~~~~~~
```
* In the 3-args case, the lengths of the arguments were not checked
* in the 3-args case, the type of the 2nd argument was not checked
* gcc falsely diagnosed a `maybe-uninitialized` variable because it
did not see that the branches of the if() statement were mutually
exclusive
It's this third issue that originally drew my attention to this code,
adafruit/circuitpython#2787
Here we actually get bugs fixed! At many sites, mp_parse_arg_all's
first argument was the number of positional arguments required, rather
than the number actually supplied.
This fixes e.g., the bug where the linspace third positional argument
was not used as the "num" argmuent, and where too many positional args
were not treated as an error:
>>> ulab.linspace(0, 1, 9)
array([0.0, 0.125, 0.25, 0.375, 0.5, 0.625, 0.75, 0.875, 1.0], dtype=float)
>>> ulab.linspace(0, 1, 1, 1)
TypeError: extra positional arguments given
In the case of argmin/argmax of an iterable, it is now signaled to the user
that only the axis=None case is supported, instead of giving a wrong
result.
A declaration of a local variable can "shadow" a parameter or another
local variable declared in an outer scope.
Since this can create confusion about which variable is referred to, it
is better to fix these diagnostics.
A variety of changes were made:
- Add curly braces to reduce the scope of a variable (ndarray_unary_op)
so that its scope has ended before the next scope where it is used
- be consistent about whether a variable is declared with for-loop scope
or not (ndarray_print_row)
- remove a declaration so that the outer variable is used, after verifying
this will function properly (insert_slice_list)
- rename a variable introduced by a macro (RUN_SUM, RUN_STD) so it does
not shadow another variable
This diagnostic flag, enabled by default in CircuitPython, requires that
nonstatic functions have a previous prototype. Since placing prototypes
in header files is the only way that mismatched arguments between function
definition and use sites can be detected, this is a valuable warning.
In the case of ulab, the majority of the changes required were to mark
functions as "static" that were used only in a single C source file.
