Re: [boost] Review Request: Variadic Macro Data library

Subject: Re: [boost] Review Request: Variadic Macro Data library
From: Edward Diener (eldiener_at_[hidden])
Date: 2011-02-20 19:56:44

On 2/18/2011 7:27 PM, Lorenzo Caminiti wrote:
> On Thu, Feb 17, 2011 at 5:13 PM, Edward Diener<eldiener_at_[hidden]>  wrote:
>> I am requesting that my library, the Variadic Macro Data library, which is
>> in the sandbox in the variadic_macro_data directory, be reviewed for
>> inclusion into Boost.
>>
>> The variadic_macro_data library adds support and functionality for variadic
>> macros to Boost as well as integrating variadic macros with the Boost PP
>> library without changing the latter library in any way.
>>
>> I believe others have used my library, can attest to its quality and that it
>> does what it is supposed to do. and have found it useful when using variadic
>> macros with Boost PP. I myself have used its functionality in my own TTI
>> library in the sandbox. Support for variadic macros is implemented in nearly
>> all modern C++ compilers and the syntax is natural for an end-user. The
>> library is finalized as far as functionality is concerned and I would like
>> to see it in Boost and am willing to maintain it as a Boost library.
>
> Is it possible to use variadic macros to detect empty parameters?
>
> For example:
>
> #include<boost/variadic_macro_data/VariadicMacroData.hpp>  // Proposed lib.
>
> VMD_DATA_SIZE(1, 2) // 2
> VMD_DATA_SIZE(1)    // 1
> VMD_DATA_SIZE()     // 1 not 0 :((
>
> But I would like to the last size to expand to 0 (or have a different
> macro that would expand to 0 in that case).
>
> With a real C99 preprocessor (e.g., GCC) I can do the following
> because empty macro parameters are supported:
>
> #include<boost/variadic_macro_data/VariadicMacroData.hpp>  // Proposed lib.
> #include<boost/preprocessor.hpp>
> #include<boost/preprocessor/facilities/is_empty.hpp>
>
> #define PP_VA_EAT(...) /* must expand to nothing */
>
> #define PP_VA_SIZE_1OR0_(x) BOOST_PP_IIF(BOOST_PP_IS_EMPTY(x), 0, 1)
>
> #define PP_VA_SIZE_(size, ...) \
>      BOOST_PP_IIF(BOOST_PP_EQUAL(size, 1), \
>          PP_VA_SIZE_1OR0_ \
>      , \
>          size PP_VA_EAT \
>      )(__VA_ARGS__)
>
> #define PP_VA_SIZE(...) PP_VA_SIZE_(VMD_DATA_SIZE(__VA_ARGS__), __VA_ARGS__)
>
> PP_VA_SIZE(1, 2)    // 2
> PP_VA_SIZE(1)       // 1
> PP_VA_SIZE()        // 0 :))

This does not work for me under gcc.

#include <boost/variadic_macro_data/vmd.hpp>
#include <boost/preprocessor.hpp>
#include <boost/preprocessor/facilities/is_empty.hpp>

#if !defined(BOOST_NO_VARIADIC_MACROS)
#define PP_VA_EAT(...) /* must expand to nothing */
#define PP_VA_SIZE_1OR0_(x) BOOST_PP_IIF(BOOST_PP_IS_EMPTY(x), 0, 1)
#define PP_VA_SIZE_(size, ...) \
     BOOST_PP_IIF(BOOST_PP_EQUAL(size, 1), \
         PP_VA_SIZE_1OR0_ \
     , \
         size PP_VA_EAT \
     )(__VA_ARGS__)
#define PP_VA_SIZE(...) PP_VA_SIZE_(VMD_DATA_SIZE(__VA_ARGS__), __VA_ARGS__)
#endif

int main()
   {
   int j = PP_VA_SIZE(2);
   return 0;
   }

Gcc:

"...patience...
...found 319 targets...
...updating 4 targets...
gcc.compile.c++ 
..\..\..\bin.v2\libs\variadic_macro_data\test\test_data_try.test\gcc-mingw-4.5.2\debug\test_data_try.o
test_data_try.cpp: In function 'int main()':
test_data_try.cpp:25:11: error: 
'BOOST_PP_IIF_BOOST_PP_COMPL_BOOST_PP_NOT_EQUAL_CHECK_BOOST_PP_NOT_EQUAL_VMD_DATA_SIZE' 
was not declared in this scope
test_data_try.cpp:25:1: error: 'BOOST_PP_NOT_EQUAL_1' was not declared 
in this scope
test_data_try.cpp:13:9: error: 'PP_VA_SIZE_1OR0_' was not declared in 
this scope
test_data_try.cpp:25:11: error: 'VMD_DATA_SIZE' was not declared in this 
scope
test_data_try.cpp:25:7: warning: unused variable 'j'

     "g++"  -ftemplate-depth-128 -O0 -fno-inline -Wall -pedantic -g 
-Wno-variadic-macros   -I"..\..\.." 
-I"C:\Programming\VersionControl\boost" -c -o 
"..\..\..\bin.v2\libs\variadic_macro_data\test\test_data_try.test\gcc-mingw-4.5.2\debug\test_data_try.o" 
"test_data_try.cpp"

...failed gcc.compile.c++ 
..\..\..\bin.v2\libs\variadic_macro_data\test\test_data_try.test\gcc-mingw-4.5.2\debug\test_data_try.o...
...skipped 
<p..\..\..\bin.v2\libs\variadic_macro_data\test\test_data_try.test\gcc-mingw-4.5.2\debug>test_data_try.exe 
for lack of 
<p..\..\..\bin.v2\libs\variadic_macro_data\test\test_data_try.test\gcc-mingw-4.5.2\debug>test_data_try.o...
...skipped 
<p..\..\..\bin.v2\libs\variadic_macro_data\test\test_data_try.test\gcc-mingw-4.5.2\debug>test_data_try.run 
for lack of 
<p..\..\..\bin.v2\libs\variadic_macro_data\test\test_data_try.test\gcc-mingw-4.5.2\debug>test_data_try.exe...
...failed updating 1 target...
...skipped 3 targets..."