Those are the same as the Linux kernel macros, and probably a bunch of
other projects. Usage:

    if (likely(condition))
        branch_likely_taken();

    if (unlikely(condition))
        branch_unlikely_taken();

Attention: those two macros convert the predicate to a boolean value.
Therefore you generally cannot use them for assignments like this:
    void *p_sys = likely (malloc (sizeof (*p_sys)));
    if (!p_sys)
        return VLC_ENOMEM;
Instead you can do this:
    void *p_sys = malloc (sizeof (*p_sys));
    if (unlikely (!p_sys))
        return VLC_ENOMEM;

Replace argument = realloc( argument, size ); with realloc_or_free() in modules/*, and while at it add assert( argument ) to mark unhandled ENOMEM conditions, also for malloc().

Introduce realloc_or_free() to src/*, and add assert() to mark unhandled ENOMEM error conditions. Allocation shrinking or otherwise handled allocations don't need realloc_or_free.

Introduce realloc_or_free(), which does what realloc() does but will free the argument if the reallocation fails. This is useful in some, but not all, use cases of realloc().

Skins2: Add x11 transparency support. Hope it sets the property on the right Window; didn't have a known transparent skin to test with.

Skins2: Cosmetics and drop const from string return as there really is no point: We're returning a fresh object.

Skins2: Move method bodies with inline tags to before where they're needed. Drop const in favour of static on power() and instead of recursing(!) make it use powf().

skins2: I fail to see why Subject (not Observer) needs to have virtual methods. If you do find a reason do tell. Observer should probably be defined inside Subject instead.

Skins2: Mostly cosmetics, some C++ style casting, factor out a scroll() in anticipation of figuring out where it belongs.

Skins2: Add (and use) template parameter typedefs so that they might be used, say, as function return types. The next commit needs this.

Skins2: Factor out duplicate code (mod), and provide a const accessor to the keymap: std::map<>::operator[] will create empty nodes if they don't exist already.

Skins2: x11_display: Replace PUT_PIXEL and BLEND_PIXEL macros with templates. Could use more testing and possibly more refactoring.

Skins2: Use vlc KEY_MODIFIER_* constants for key modifier masks, simplifying the code. Revert from enum to static const int to not have to include vlc_keys.h through the header file.

Skins2: Factor out getModKey() and getKeyState() (both used twice), use var_SetVariant() instead of var_Set().

Skins2: Refactor string manipulation event handling a bit and replace some static const members with an enum.