From: Hartmut Kaiser (hartmut.kaiser_at_[hidden])
Date: 2005-12-04 11:59:39
Vambola Kotkas wrote:
> Wave Driver C++ preprocessor seems quite useful tool to see what
> happens with most macros. Unfortunatelly it needs some debugging
> before it can be used to preprocess real code. For example it refuses
> (unneccessarily) to process sometimes.
> Silly example 1:
> #if __LINE__ == 11112223334
> #pragma message( "Huh!" )
> test.cpp(1): error: ill formed integer literal or integer constant
> large: 11112223334.
> None of the available wave flags did seemingly help. Not that i need
> huge integers, however boost sometimes does have way bigger ones so it
> must be legal? MS Visual C++ 7.1 processes constants like
> 18446744073709551615 without any noise.
> See ... 1.33.0 boost/cstdint.hpp line(263):
> # if ULONG_MAX == 18446744073709551615 // 2**64 - 1
It's not legal for 32 bit systems. Either flag the 11112223334 with the LL
suffix (and the --long_long command line option) or you are out of luck with
Wave. At least as long the code is not hidden inside a non-evaluated
#if/#endif block. I've fixed Wave after 1.33.0 to accept large numbers in
non-evaluated #if expressions, just to allow to compile Boost.
> Silly example 2:
> #define SHOW2(x) #x
> #define SHOW(x) SHOW2(Number is:##x)
> #pragma message( SHOW(__LINE__))
> test.cpp(3): error: pasting the following two tokens does not give a
> valid preprocessing token: ":" and "__LINE__"
Concatenating two unrelated tokens isn't allowed by the C++ Standard. If you
really need this just provide the --variadics command line option, which
will enable certain C99 features in C++ (variadics, token concatination of
unrelated tokens etc.)
> Maybe its buggy and MS made its preprocessor too lousy there ... just
> for reference Visual C++ 7.1 preprocess result:
Yes, the MSVC preprocessor is lousy.
> Side question: How to force wave to use full paths in #line
> Larger projects may contain similarily named files and people
> usually have multiple versions of their own software, nothing
> to talk of libraries and SDK-s.
Wave does use full paths in #line directives as long as the corresponding
files are not in the directory of the main file.
> Silly thing 2 can be
> transformed into Working thing 2:
> #define SHOW2(x) #x
> #define SHOW(x) SHOW2(x)
> #pragma message("Number is:" SHOW(__LINE__)) Wave produces
> same output as VC++ 7.1 then:
> #line 3 "test.cpp"
> #pragma message("Number is:" "3")
What's silly here?
> Finally ... fair test for preprocessor is if it preprocesses
> its own code.
> That makes wave to crash with "unexpected exception caught."
> Various sets of -P and -D options make it to crash in various
> places. I did not manage to find a good set of options so it
> does not crash. How to compile debug version of wave with
bjam "-sBUILD=<debug>" ...
> Without debugging it is hard to further track down
> what is going on there. I tried the wave in boost 1.33.0.
Frankly speaking, I haven't done this for a long time. So I tried today and
got several errors/warnings reported by Wave (which I have to investigate
further), but I didn't get any segfault! I'll report on this list with my
Could you please elaborate on which compiler you used to generate Wave,
which command line options did you use?
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