Copy construction between Span of compatible type is allowed to fulfil the use
case Span<T> -> Span<const T>. This is achieved by a templated copy constructor
like constructor.
In p0122, the overload is discarded from the constructor set if the ElementType
of the Span in input is not convertible into the ElementType of the Span being
constructed.
To discard function overload, SFINAE has to be used which polutes the documentation
and make the code harder to read and maintain.
Unlike p0122, our Span class doesn't exposes (yet) functions with default argument
or functions that convert container in input into span the only overload with the
a single parameter that we exposes are:
- template<size_t N> Span(ElementType (&element)[N])
- Span(const Span& other): <- generated by the compiler.
For both of this functions we expect exact match and their resolution should not
interfere with the constructor that converts from another type of Span.
As a result it is possible to rely solely on C++ default resolution rules as we
won't hit cases were constructors convert from another type (std::array, std
container, span) and raise an error with a static assert if the element type
can't be converted.
If another copy - conversion - constructor is added then SFINAE has to be
reintroduced.
This commit aims to make Span implementation more in line with what is present in N4762:
- use appropiate index types where applicable.
- use typedefed type inside the class (index_type, reference, pointer, element_type)
- assertion where applicable
- restrict default construction to Span with extent == 0 or extent == dynamic.
- construct span from a range of pointer
- remove non const overload of the subscript operator
- remove non const overload of the data function
- implement subspan function
- implement missing first and last function of dynamic span
The Span class allows the creation of views over contiguous memory. The view
do not own memory, is typed and has a length. It can be used as a replacement of
the traditional pair of pointer and size in parameters or class fields.
Main operations:
- size(): return the lenght of the memory viewed
- empty(): return if the memory viewed is empty
- [index]: access elements viewed
- data(): return a pointer to the memory viewed.
- first(count): Create a subview from the first count elements.
- last(count): Create a subview from the last count elements.
- == and !=: compare two views or a view to array and return if they are equal or
not.
The Span class came in two flavors:
- Static size: The size is encoded in the Span type and it is as lightweitgh as
a single pointer,
- Dynamic size: The object can store arbitrary views and it costs one pointer
and the size of the view.
When the define LPTICKER_DELAY_TICKS is set deep sleep can be randomly
disallowed when using the low power ticker. This is because a Timer
object, which locks deep sleep, is used to protect from back-to-back
writes to lp tickers which can't support that. This causes tests which
assert that deep sleep is allowed to intermittently fail.
To fix this intermittent failure this patch adds the function
sleep_manager_can_deep_sleep_test_check() which checks if deep sleep
is allowed over a duration. It updates all the tests to use
sleep_manager_can_deep_sleep_test_check() rather
than sleep_manager_can_deep_sleep() so the tests work even if deep
sleep is spuriously blocked.
Volatile specifier in this case it not required as we currently have all accesses
to the buffer protected by critical section. This shall optimize accesses in
some cases to the buffer.
Fixes#7702
`handle_error` calls `MBED_CALLER_ADDR()`, but this is always a location from within platform/mbed_error.c. This is because `handle_error` is declared static. This does not cause the function to be inlined however. Instead, it is called by each function within mbed_error.c. For example, mbed_error yields this code:
```
000625c8 <mbed_error>:
625c8: b510 push {r4, lr}
625ca: 460c mov r4, r1
625cc: 4611 mov r1, r2
625ce: 461a mov r2, r3
625d0: 9b02 ldr r3, [sp, #8]
625d2: f7ff feff bl 623d4 <handle_error>
625d6: b968 cbnz r0, 625f4 <mbed_error+0x2c>
625d8: 4620 mov r0, r4
625da: f7ff ff67 bl 624ac <print_error_report.constprop.0>
625de: f7ff fea8 bl 62332 <core_util_is_isr_active>
625e2: b910 cbnz r0, 625ea <mbed_error+0x22>
625e4: f7ff fe9f bl 62326 <core_util_are_interrupts_enabled>
625e8: b908 cbnz r0, 625ee <mbed_error+0x26>
625ea: bf30 wfi
625ec: e7fd b.n 625ea <mbed_error+0x22>
625ee: 2001 movs r0, #1
625f0: f000 f948 bl 62884 <__wrap_exit>
625f4: 4800 ldr r0, [pc, #0] ; (625f8 <mbed_error+0x30>)
625f6: bd10 pop {r4, pc}
625f8: 80ff010f .word 0x80ff010f
```
Note that at `625d2` there is a bl to handle error. That replaces the LR, which means that ALL calls to mbed_error will report a location of 0x625d6 or 0x625d7 (user vs. supervisor). I do not expect that this was the intention of the code. The simplest fix is to change line 99:
```C
static inline mbed_error_status_t handle_error(mbed_error_status_t error_status, unsigned int error_value, const char *filename, int line_number)
```
Since `handle_error()` will be inlined, the link register will be kept the same, so `MBED_CALLER_ADDR()` will yield the expected result. However, there is no guarantee that the compiler will respect the `inline` keyword in all circumstances.
The result is that each function that wishes to report its caller must extract its caller. This code cannot be centralised.
I have modified `mbed_error.c` to report the caller of each error reporting function, rather than the error reporting function itself.
Cruz Monrreal
Vincent Coubard
Amanda Butler
Martin Kojtal
Oren Cohen
Donatien Garnier
Russ Butler
David Saada
kegilbert
Brendan Moran
ccli8
Senthil Ramakrishnan
Deepika