Revert part of "DRTVWR-575: Address review comments on Xcode 14.1 type tweaks."
Crash was reproduced when assigning areastr to llsd, but likely present in other cases of assigning ui strings to llsd (instead of going for lluistring's result directly copy constructor was engaged and either copy or original crashed due to invalid pointers, copy shouldn't have been created).
One could argue that passing a negative index to an LLSD array should do
something other than shrug and reference element [0], but as that's legacy
behavior, it seems all too likely that the viewer sometimes relies on it.
This specific problem arises if the index passed to operator[]() is negative
-- either with the previous Integer parameter or with size_t (which of course
reinterprets the negative index as hugely positive). The non-const
ImplArray::ref() overload checks parameter 'i' and, if it appears negative,
sets internal 'index' to 0.
But in the next stanza, if (index >= existing size()), it calls resize() to
scale the internal array up to one more than the requested index. The trouble
is that it passed resize(i + 1), not the adjusted resize(index + 1).
With a requested index of exactly -1, that would pass resize(0), which would
result in the ensuing array[0] reference being invalid.
With a requested index less than -1, that would pass resize(hugely positive)
-- since, whether operator[]() accepts signed LLSD::Integer or size_t,
resize() accepts std::vector::size_type. Given that the footprint of an LLSD
array element is at least a pointer, the number of bytes required for
resize(hugely positive) is likely to exceed available heap storage.
Passing the adjusted resize(index + 1) should defend against that case.
LLFloaterLandHoldings::postBuild() was constructing an LLSD structure by
assigning each map entry and array element one at a time. Chorazinallen
identified a crash bug possibly caused by destroying that LLSD structure.
Diagnostically try building it using nested llsd::map() and llsd::array()
calls instead to see if that improves matters.
The compiler was deducing an unsigned type for the difference (U64 desired
microseconds - half KERNEL_SLEEP_INTERVAL_US). When the desired sleep was less
than that constant, the difference went hugely positive, resulting in a very
long snooze.
Amusingly, forcing that U64 result into an S32 num_sleep_intervals worked only
*because* of integer truncation: the high-order bits were discarded, resulting
in a negative result as intended.
Ensuring that both integer operands are signed at the outset, though, produces
a more formally correct result.
It seems newer compilers have a different interpretation of exactly when to
engage LLSDArray's copy constructor. In particular, this assignment:
some_LLSD_map[key] = LLSDArray(...)(...)...;
used to convert the LLSDArray object directly to LLSD; now it first calls the
custom copy constructor, which embeds the intended array within an outer array
before assigning it into the containing map.
The newer llsd::array() function avoids that problem because what it returns
is already an LLSD object.
Taking inventory of LLSDArray assignments of that form turned up a number of
workarounds like LLSD(LLSDArray(...)). Replacing those with llsd::array() is
both simpler and more readable.
Tip of the hat to Chorazinallen for surfacing this issue!
Callum Prentice