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List: boost
Subject: Re: [boost] [Config] boost::uint32_t != std::uint32_t on some targets
From: Christopher Kormanyos <e_float () yahoo ! com>
Date: 2015-11-23 19:31:07
Message-ID: 1676027353.8839271.1448307067166.JavaMail.yahoo () mail ! yahoo ! com
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> > I recently fell into a trap where a program wouldn't compile because of a>> \
> > difference between `boost::uint32_t` and `std::uint32_t`. Specifically, I>> was \
> > trying to cross-compile from OS X to ARM, and the following program>> wouldn't \
> > compile>>>> #include <boost/cstdint.hpp>>> #include <cstdint>>> \
> > #include <type_traits>>>>> static_assert(std::is_same<std::uint32_t, \
> > boost::uint32_t>::value, "");
> boost/cstdint.hpp is based on stdint.h or inttypes.h when possible -
> presumably, as well as cstdint. So I'd say the intention is for the
> integer typedefs to be the same.
I prefer to test with compile-time assert on the number of binary digitsin the type, \
as given in <limits>. For example: #include <cstdint>
#include <limits>
#include <type_traits>
#include <boost/cstdint.hpp>
static_assert(std::numeric_limits<boost::unit32_t>::digits == 32, "Error: wrong digit \
count for boost::uint32_t."); \
static_assert(std::numeric_limits<std::unit32_t>::digits == 32, "Error: wrong digit \
count for std::uint32_t.");
This is because either of boost::uint32_t or std::uint32_t on ARMmight use a type \
like unsigned long, or unsigned int under-the-hood,and these may disagree for a \
different compiler. It gets even worse when porting to an 8-bit platform whereint \
might have 8 bits or 16 bits and a 32 bit integer typemight need long or long long. \
Cheers, Chris
On Monday, November 23, 2015 11:51 AM, Andrey Semashev \
<andrey.semashev@gmail.com> wrote:
On 2015-11-22 20:24, Louis Dionne wrote:
> Dear Boost,
>
> I recently fell into a trap where a program wouldn't compile because of a
> difference between `boost::uint32_t` and `std::uint32_t`. Specifically, I
> was trying to cross-compile from OS X to ARM, and the following program
> wouldn't compile
>
> #include <boost/cstdint.hpp>
> #include <cstdint>
> #include <type_traits>
>
> static_assert(std::is_same<std::uint32_t, boost::uint32_t>::value, "");
>
> int main() { }
>
>
> I was building with
>
> arm-none-eabi-g++ -I /path/to/boost -std=c++11 -c main.cpp
>
>
> I have asked a question on StackOverflow [1], and I now understand why the
> two types are not required to be the same. However, I think it is a QOI
> issue that those two types are not the same, since it makes interoperating
> between `std::uint32_t` and `boost::uin32_t` more difficult. Is there a
> reason for this difference, and if not would it be reasonable to ensure that
> `boost::uint32_t == std::uint32_t` whenever the latter is defined, i.e. in
> C++11 and above?
boost/cstdint.hpp is based on stdint.h or inttypes.h when possible -
presumably, as well as cstdint. So I'd say the intention is for the
integer typedefs to be the same.
My guess is that the problems is caused by BOOST_HAS_STDINT_H not
defined on your platform. If you have a usable stdint.h then this macro
should be defined and the problem should go away. Otherwise the platform
should be detected directly in boost/cstdint.hpp. In any case it would
be easier if you could prepare a PR.
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