Re: g_error_free() warning on null pointer

Simon McVittie wrote:
On 16/08/15 20:23, Michael McConville wrote:
Emmanuele Bassi wrote:
You expected the *_free() functions in GLib to be NULL-safe. They
aren't, except for g_free().

g_error_free is. Maybe others too, I haven't checked. It just prints
annoying console warnings.

The intention throughout the GLib-based stack is that if a
g_return[_val]_if_fail() is hit, it indicates that the caller has
called the function incorrectly, in a way that is considered to be
undefined behaviour
<>. Undefined
behaviour does not mean "your code will crash"; it means "any result
is valid, and it is up to the compiler or library author what
happens". It does in practice end up meaning "your code is wrong",
because the majority of the possible implementations of undefined
behaviour are not what you wanted.

I still don't understand how this is relevant. I already understand what
undefined behavior is and how it relates to compilers/optimization.
However, this sort of smoke and mirrors inexactness doesn't apply to
GLib - there's a single implementation and we can just go and look at
the source code and see what it does. In the case of g_error_free, this

 1) print an annoying warning
 2) call g_free(), which is NULL-safe
 3) call g_slice_free(), which is NULL-safe

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