Re: Updating from 1_71_0 to 1_85_0: "No member named 'memcpy' in namespace 'std::__1'"

From: Alexander Grund (alexander.grund_at_[hidden])
Date: 2024-07-11 07:07:08

> When updating from Boost 1_71_0 to 1_85_0, I’m suddenly encountering these kinds of errors:
This looks like something else was updated too as most errors look like 
compiler/std-library issues:
> /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.3.sdk/usr/include/c++/v1/__functional/hash.h:40:5: No member named 'memcpy' in namespace 'std::__1'; did you mean simply 'memcpy'?
This is an error originating from libc++ installed on the system not 
even Boost. If they don't provide it in their own namespace I don't see 
much that Boost can do, if anything at all.
> /Users/stephen/dev/Boost Libraries/boost_1_85_0/boost/system/detail/append_int.hpp:23:5: No member named 'snprintf' in namespace 'boost::system::detail'; did you mean simply 'snprintf'?
That looks related.
https://github.com/boostorg/system/blob/boost-1.85.0/include/boost/system/detail/snprintf.hpp#L22C12-L22C20 
has a `using std::snprintf;` to pull in snprintf to boost::system::detail
If that doesn't exist in std then I even wonder how the header compiles 
in the first place.
In this case there is a change in Boost 1.85 though replacing a custom 
snprintf by a using. However `std::snprintf` is only available since 
C++11. Are you not compiling with that or higher?
> /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.3.sdk/usr/include/c++/v1/__functional/hash.h:40:5: error: no member named 'memcpy' in namespace 'std::__1'; did you mean simply 'memcpy'?
Same as first.
> Showing All Errors Only
>
> /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.3.sdk/usr/include/c++/v1/filesystem:2635:5: Use of undeclared identifier '_LIBCPP_UNREACHABLE'
Similarly a strong hint the installed libc++ might be broken

So first make sure the C++ standard of your compilation is >= C++11.