Compatibility

The library supports several Lua versions listed below. By default the library selects the most recent API version known to it.

Lua 5.1

Also compatible with LuaJIT. Turned on with LUAPP_COMPATIBILITY_V51 macro.

Lua 5.2

Turned on with LUAPP_COMPATIBILITY_V52.

Differences to mode 5.1:

• Lua-side arithmetics is enabled for value objects;
• length operation returns Lua value instead of native size_t;
• the gcIsRunning function is available;
• the getVersion function is available;
• the raw accessor uses specialized rawgetp/rawsetp functions for pointer-type indices.

Lua 5.3

Turned on by default or with LUAPP_COMPATIBILITY_V53.

Differences to mode 5.2:

• native integer types are promoted to Lua number/integer subtype;
• values have linked accessor to associated value (only userdata can have something associated with it);
• additional Lua-side operations are available: integer division, bitwise AND, bitwise OR, bitwise XOR, bitwise NOT, shift bits left, shift bits right;
• indexing values with native integer types now uses specialized geti/seti functions;
• optcast is no longer available (it was superseded by to with argument).

NRVO compiler capability

NRVO is a compiler feature, extension of RVO (return value optimization). RVO in short means that if a function returns anonymous value, it won't be copied into result but rather constructed in-place. NRVO (named RVO) means that same thing can be done with named variable. This feature, if supported by compiler, allows to return anchors from functions by value. Some tests and getUpvalues function depend on it and will be disabled if LUAPP_COMPATIBILITY_NO_NRVO macro is used.