Hi,
|jsid| is a struct in debug builds and an integral type in opt builds.
From jspubtd.h:
/*
* In release builds, jsid is defined to be an integral type. This
* prevents many bugs from being caught at compile time. E.g.:
*
* jsid id = ...
* if (id) // error
* ...
*
* size_t n = id; // error
*
* To catch more errors, jsid is given a struct type in C++ debug builds.
* Struct assignment and (in C++) operator== allow correct code to be mostly
* oblivious to the change. This feature can be explicitly disabled in debug
* builds by defining JS_NO_JSVAL_JSID_STRUCT_TYPES.
*/
# if defined(DEBUG) && !defined(JS_NO_JSVAL_JSID_STRUCT_TYPES)
# define JS_USE_JSID_STRUCT_TYPES
# endif
# ifdef JS_USE_JSID_STRUCT_TYPES
struct jsid
{
size_t asBits;
bool operator==(jsid rhs) const { return asBits == rhs.asBits; }
bool operator!=(jsid rhs) const { return asBits != rhs.asBits; }
};
# define JSID_BITS(id) (id.asBits)
# else /* defined(JS_USE_JSID_STRUCT_TYPES) */
typedef ptrdiff_t jsid;
# define JSID_BITS(id) (id)
# endif /* defined(JS_USE_JSID_STRUCT_TYPES) */
I'm wondering if this whole game is even necessary. Could we use the
struct version in opt builds as well? The only reason I can think not
to is if some compilers do not optimize a struct containing a single
integer as well as they would a naked integer.
Relatedly, the explicit operator== and operator!= functions appear to
be the same as what the default versions would be.
Nick
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