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I think that C++ should require that the standard macros imported from C
support templated types with commas in them, and similar expressions.  With
__VA_ARGS__, this is easy to do in all but one case.

Like this:

template <typename TX, typename TY>
struct Meow
{
    bool SomeFunc() const;
    TX m_x;
    TY m_y;
};

int main()
{
    assert(Meow<int, double>().SomeFunc());
    std::printf("%zu\n", offsetof(Meow<char *, short>, m_y));
}


Among the standard macros, offsetof() is the weird case.  Implementing it
in some environments would require supporting up to a particular number of
parameters using macro tricks, since you need to get the last parameter
separately from the others.  In some environments, such as GCC and Clang,
this is trivial to implement, because passing all arguments straight
through to __builtin_offsetof() would cause the arguments to be parsed in
C++ fashion.  As far as I can think of, it is never necessary to have
commas in the second parameter of offsetof().

Melissa

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<div dir=3D"ltr">I think that C++ should require that the standard macros i=
mported from C support templated types with commas in them, and similar exp=
ressions.=C2=A0 With <span style=3D"font-family: courier new,monospace;">__=
VA_ARGS__</span>, this is easy to do in all but one case<span style=3D"font=
-family: courier new,monospace;"></span>.<br><br>Like this:<br><br><div cla=
ss=3D"prettyprint" style=3D"background-color: rgb(250, 250, 250); border-co=
lor: rgb(187, 187, 187); border-style: solid; border-width: 1px; word-wrap:=
 break-word;"><code class=3D"prettyprint"><div class=3D"subprettyprint"><sp=
an style=3D"color: #008;" class=3D"styled-by-prettify">template</span><span=
 style=3D"color: #000;" class=3D"styled-by-prettify"> </span><span style=3D=
"color: #660;" class=3D"styled-by-prettify">&lt;</span><span style=3D"color=
: #008;" class=3D"styled-by-prettify">typename</span><span style=3D"color: =
#000;" class=3D"styled-by-prettify"> TX</span><span style=3D"color: #660;" =
class=3D"styled-by-prettify">,</span><span style=3D"color: #000;" class=3D"=
styled-by-prettify"> </span><span style=3D"color: #008;" class=3D"styled-by=
-prettify">typename</span><span style=3D"color: #000;" class=3D"styled-by-p=
rettify"> TY</span><span style=3D"color: #660;" class=3D"styled-by-prettify=
">&gt;</span><span style=3D"color: #000;" class=3D"styled-by-prettify"><br>=
</span><span style=3D"color: #008;" class=3D"styled-by-prettify">struct</sp=
an><span style=3D"color: #000;" class=3D"styled-by-prettify"> </span><span =
style=3D"color: #606;" class=3D"styled-by-prettify">Meow</span><span style=
=3D"color: #000;" class=3D"styled-by-prettify"><br></span><span style=3D"co=
lor: #660;" class=3D"styled-by-prettify">{</span><span style=3D"color: #000=
;" class=3D"styled-by-prettify"><br>=C2=A0 =C2=A0 </span><span style=3D"col=
or: #008;" class=3D"styled-by-prettify">bool</span><span style=3D"color: #0=
00;" class=3D"styled-by-prettify"> </span><span style=3D"color: #606;" clas=
s=3D"styled-by-prettify">SomeFunc</span><span style=3D"color: #660;" class=
=3D"styled-by-prettify">()</span><span style=3D"color: #000;" class=3D"styl=
ed-by-prettify"> </span><span style=3D"color: #008;" class=3D"styled-by-pre=
ttify">const</span><span style=3D"color: #660;" class=3D"styled-by-prettify=
">;</span><span style=3D"color: #000;" class=3D"styled-by-prettify"><br>=C2=
=A0 =C2=A0 TX m_x</span><span style=3D"color: #660;" class=3D"styled-by-pre=
ttify">;</span><span style=3D"color: #000;" class=3D"styled-by-prettify"><b=
r>=C2=A0 =C2=A0 TY m_y</span><span style=3D"color: #660;" class=3D"styled-b=
y-prettify">;</span><span style=3D"color: #000;" class=3D"styled-by-prettif=
y"><br></span><span style=3D"color: #660;" class=3D"styled-by-prettify">};<=
/span><span style=3D"color: #000;" class=3D"styled-by-prettify"><br><br></s=
pan><span style=3D"color: #008;" class=3D"styled-by-prettify">int</span><sp=
an style=3D"color: #000;" class=3D"styled-by-prettify"> main</span><span st=
yle=3D"color: #660;" class=3D"styled-by-prettify">()</span><span style=3D"c=
olor: #000;" class=3D"styled-by-prettify"><br></span><span style=3D"color: =
#660;" class=3D"styled-by-prettify">{</span><span style=3D"color: #000;" cl=
ass=3D"styled-by-prettify"><br>=C2=A0 =C2=A0 </span><span style=3D"color: #=
008;" class=3D"styled-by-prettify">assert</span><span style=3D"color: #660;=
" class=3D"styled-by-prettify">(</span><span style=3D"color: #606;" class=
=3D"styled-by-prettify">Meow</span><span style=3D"color: #660;" class=3D"st=
yled-by-prettify">&lt;</span><span style=3D"color: #008;" class=3D"styled-b=
y-prettify">int</span><span style=3D"color: #660;" class=3D"styled-by-prett=
ify">,</span><span style=3D"color: #000;" class=3D"styled-by-prettify"> </s=
pan><span style=3D"color: #008;" class=3D"styled-by-prettify">double</span>=
<span style=3D"color: #660;" class=3D"styled-by-prettify">&gt;().</span><sp=
an style=3D"color: #606;" class=3D"styled-by-prettify">SomeFunc</span><span=
 style=3D"color: #660;" class=3D"styled-by-prettify">());</span><span style=
=3D"color: #000;" class=3D"styled-by-prettify"><br>=C2=A0 =C2=A0 std</span>=
<span style=3D"color: #660;" class=3D"styled-by-prettify">::</span><span st=
yle=3D"color: #000;" class=3D"styled-by-prettify">printf</span><span style=
=3D"color: #660;" class=3D"styled-by-prettify">(</span><span style=3D"color=
: #080;" class=3D"styled-by-prettify">&quot;%zu\n&quot;</span><span style=
=3D"color: #660;" class=3D"styled-by-prettify">,</span><span style=3D"color=
: #000;" class=3D"styled-by-prettify"> offsetof</span><span style=3D"color:=
 #660;" class=3D"styled-by-prettify">(</span><span style=3D"color: #606;" c=
lass=3D"styled-by-prettify">Meow</span><span style=3D"color: #660;" class=
=3D"styled-by-prettify">&lt;</span><span style=3D"color: #008;" class=3D"st=
yled-by-prettify">char</span><span style=3D"color: #000;" class=3D"styled-b=
y-prettify"> </span><span style=3D"color: #660;" class=3D"styled-by-prettif=
y">*,</span><span style=3D"color: #000;" class=3D"styled-by-prettify"> </sp=
an><span style=3D"color: #008;" class=3D"styled-by-prettify">short</span><s=
pan style=3D"color: #660;" class=3D"styled-by-prettify">&gt;,</span><span s=
tyle=3D"color: #000;" class=3D"styled-by-prettify"> m_y</span><span style=
=3D"color: #660;" class=3D"styled-by-prettify">));</span><span style=3D"col=
or: #000;" class=3D"styled-by-prettify"><br></span><span style=3D"color: #6=
60;" class=3D"styled-by-prettify">}</span><span style=3D"color: #000;" clas=
s=3D"styled-by-prettify"><br></span></div></code></div><br><br>Among the st=
andard macros, <span style=3D"font-family: courier new,monospace;">offsetof=
()</span> is the weird case.=C2=A0 Implementing it in some environments wou=
ld require supporting up to a particular number of parameters using macro t=
ricks, since you need to get the last parameter separately from the others.=
=C2=A0 In some environments, such as GCC and Clang, this is trivial to impl=
ement, because passing all arguments straight through to <span style=3D"fon=
t-family: courier new,monospace;">__builtin_offsetof()</span> would cause t=
he arguments to be parsed in C++ fashion.=C2=A0 As far as I can think of, i=
t is never necessary to have commas in the second parameter of <span style=
=3D"font-family: courier new,monospace;">offsetof()</span>.<br><br>Melissa<=
br></div>

<p></p>

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