Re: [PATCH 1/2] pkt-line: fix declaration of `set_packet_header()`

[Junio C Hamano <gitster@pobox.com>]

Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:

>> lacked the "const" for that reason, but apparently some compilers
>> complain about the parameter type mismatch.
>
> We could be more explicit, as we know exactly that it is MS Visual C 2017
> that is complaining.

We could be, but I do not see a point of shaming one particular
compiler vendor.

>> Let's squelch it by removing the "const" that is pointless for a
>> small function like this, which would not help optimizing compilers
>
> It is not pointless because of the size of the function, but because `int`
> is already a type that is always passed by value, never by reference.

You are looking only at the prototype side (i.e. declaration in
*.h).  Yes it is pointless for the callers.  For the callee, the
story is different and pass-by-value does not even get in the
picture.

The mention of pointless-ness I made was about the implementation
side (i.e. definition in *.c).  For a sufficiently large and complex
function implementation, being able to say upfront that this
incoming parameter is never modified would help following the logic
in the implementation, so "const int param" in the parameter list of
a definition is *not* pointless in general.  But apparently some
compilers are not happy abot "const int param" in implementation
that is paired with "int param" in prototype, we are dropping a
const that could be useful, with an excuse that for this particular
function that is small and trivial, we can live without.