[Jsoncpp-devel] Identified portability issues and solutions

[Baptiste L. <bap...@gm...>]

I though I would share the portability issues I run into and fixed the last
few days:

- Do not use STL API that requires special handling of 64 bits integers.
Those can lead to interesting errors (MSVC 6 is a typical example):
  My understanding is that the initial STL standard did not acknoledge the
existence of 64 bits integers and STL implementor did not extend the API on
their own...
  - std::ostream do not support 64 bits integer, leading to ambiguous
overload compilation error
  - std::numeric_limits<> compiles but returns 0 at run_time
- Do not rely on formatting of floating point numbers as string:
  MSVC typically always output 3 digits in the exponent, Unix platforms have
a varying number of digits
  (This was solved by introducing the normalizeFloatingPointStr() function
to normalize the formatting of the floating-point exponent)
- uint64 to double conversion is trouble:
  Unfortunately no generic recipes. Requires multi-platform testing when
introducing new use cases...
  - not supported by MSVC6 (worked-around by using int64 to double
conversion)
  - can run into interesting precision issues when comparing double stored
in local variable and FPU registers (that may be of greater precision)
  - some strange issue when converting uint64 max to double on the very old
XLC 7 compiler (produced -1...)
- Do not use LL and ULL for 64 bits literal
  Unfortunately not supported by all compilers (MSVC 6 for instance).
  - work-around this by converting an integer to int64. Example: UInt64(1)
<< 63

Baptiste.