Reference: https://gcc.gnu.org/gcc-4.9/porting_to.html
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Header <cstddef> changes
The <cstddef> header was updated for C++11 support and this breaks some
libraries which misuse macros meant for internal use by GCC only. For
instance with GMP versions up to 5.1.3, you may see:
/usr/include/c++/4.9.0/cstddef:51:11: error: ‘::max_align_t’ has not been declared
using ::max_align_t;
^
Another possible error is:
someheader.h:99:13: error: ‘ptrdiff_t’ does not name a type
A workaround until libraries get updated is to include <cstddef> or
<stddef.h> before any headers from that library.
This commit allows us to build Lean without the pthread dependency.
It is also useful if we want to implement multi-threading on top of Boost.
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
