My code is compiled using the g++ compiler version 4.9.0. I'm using C++11.
However, the compiler doesn't understand the nullptr keyword. Here is what I've found out:
This is not a typo, because the word nullptr is displayed in bold in the editor.
g++ supports nullptr, because its version is greater than 4.6.0.
The compiler understands that I want to use C++11, because it doesn't complain when I use auto or decltype one line earlier (I use the -std=c++0x command-line argument, but I also the -std=gnu++0x).
I have no idea what else can be wrong, so I'll be grateful for any suggestions.
Edit: the error message is the following:
error: nullptr was not declared in this scope.
This is the output of the
g-- version command:
g++ (OSE 4.9.2-2 20160202) 4.9.2
The flag in recent versions of g++ is -std=c++11.
My code is compiled using the g++ compiler version 4.9.0. I'm using C++11.
No it isn't, it's being compiled with GCC 4.5, or older. Otherwise nullptr would work.
This is the output of the g-- version command:
g++ (OSE 4.9.2-2 20160202) 4.9.2
Well that's certainly not 4.9.0, what is OSE?
How are you compiling your code? Because it seems to be finding a different version of GCC, not that one.
Related
I am trying to build cmake source, which requires C++11.
The build halts and apparently the complaint is that C++11 is not detected. The g++ mode is actually set to -std=gnu++17
This is part of the console log
---------------------------------------------
CMake 3.18.20200919, Copyright 2000-2020 Kitware, Inc. and Contributors
Found GNU toolchain
C compiler on this system is: gcc
C++ compiler on this system is: g++ -std=gnu++17
Makefile processor on this system is: make
g++ has setenv
g++ has unsetenv
g++ does not have environ in stdlib.h
g++ has stl wstring
g++ has <ext/stdio_filebuf.h>
---------------------------------------------
g++ -std=gnu++17 -DCMAKE_BOOTSTRAP -DCMake_HAVE_CXX_MAKE_UNIQUE=1 -c $HOME/Apps/CMake-master/Source/cmAddCustomCommandCommand.cxx -o cmAddCustomCommandCommand.o
This is part of the error in the log file...
In file included from /usr/include/c++/5/unordered_map:35:0,
from cmake_bootstrap_11920_test.cxx:4:
/usr/include/c++/5/bits/c++0x_warning.h:32:2: error: #error This file requires compiler and library support for the ISO C++ 2011 standard. This support must be enabled with the -std=c++11 or -std=gnu++11 compiler options.
#error This file requires compiler and library support \
^
cmake_bootstrap_11920_test.cxx:7:2: error: #error "Compiler is not in a mode aware of C++11."
#error "Compiler is not in a mode aware of C++11."
^
cmake_bootstrap_11920_test.cxx:70:16: warning: non-static data member initializers only available with -std=c++11 or -std=gnu++11
int Member = 1;
Looking around on the web, I noticed that C++11 is only available after gcc version 4.6.
I checked my version, and it seems to be above.
g++ --version
g++ (Ubuntu 5.4.0-6ubuntu1~16.04.12) 5.4.0 20160609
I understand the -std=c++11 flag is used to enable the C++11 features in g++, but I don't seem to know what I am doing in this case.
I tried editing the CompileFlags.cmake file, but no change occurs.
I came upon this page which points to the cmake source I am using.
It says...
bootstrap: Require compiler mode aware of C++11
Some compilers have enough features enabled in their default modes to
pass our simple C++11 unique_ptr check but do not enable enough to build
CMake. Poison this case so that we choose one of the explicit `-std=`
options for such compilers.
Not sure what that means exactly.
How exactly do I change the g++ mode, to C++11, so that on running the bootstrap command, C++11 is used?
Or, in other words, how do I change std to point to C++11 (-std=c++11)?
First of all, you have g++ version 5.4.0 in your host PC installed, which is good, cause it means this is also supports the C++11, which you want to use.
To set it up, you could define it in your CMakeList.txt file:
set (CMAKE_CXX_STANDARD 11)
that should do the trick.
Please also check the documentation:
https://cmake.org/cmake/help/v3.1/variable/CMAKE_CXX_STANDARD.html
Usually, I would suggest to use the latest standard that you compiler is supporting (https://gcc.gnu.org/projects/cxx-status.html), cause you'll get also the latest features introduced in that standard. Exception for this rather in case you are working with legacy codes.
I am trying to configure the last version of clang (6.0) to use the arm-none-eabi linker instead of the ld.lld but clang is always ignoring everything and keep asking for the ld.lld one. I am trying to build for cortex-m3 (lpx1769 board). How do I force clang to use the linker I want.
-fuse-ld=ld is also not working, so does clang no longer allow the use of any other linker?
So the answer was to use the flag:
-fuse-ld=path/to/linker-to-be-used
Remember that if you passing this flag to clang it will cause a warning that clang will not use this flag (only the linker stage will do). Thus if you compiling with -Werror, the warning will be turned into an error.
Moreover, because you are cross-compiling probably you will need to let the linker know where to find the target-specific libraries needed using the -L option. See this for more info:
https://clang.llvm.org/docs/CrossCompilation.html
I've recently downloaded CUDA 7 and set it up to work with my project. On Mac, CUDA 7 requires clang to be the host compiler.
Now, I'm using a number of C++11 features. I've enabled these with -std=c++11 passed to nvcc this works. However, if I pass -Xcompiler -std=c++11 to nvcc, I get the following error regardless of if I also passed -std=c++11 by itself. The error is:
"invalid argument '-std=c++11' not allowed with 'C/ObjC'"
It seems like this should work, it certainly does with GCC. Anyone have a workaround. Otherwise, I'll file a bug report with Nvidia.
nvcc -dryrun ... will show what commands nvcc will execute. I don't currently have access to CUDA 7, only 6.5, but mine issues, among other things, two commands that compiles generated C source. This code generated by cudafe and have to be compiled by C compiler, but -Xcompiler adds options for both C and C++ modes.
I guess difference with my gcc situation is that I'm getting a warning while you have an error (this is exactly how gcc and clang differs in that case). For both compilers I don't see any way to suppress it, so I guess you have to fix your .cmake files to omit -Xcompiler options. This options shouldn't be used for language standard, just some very compiler-specific things.
Of course it doesn't work. You are specifying C++ options while using a C or Objective-C compiler. The source files must be C++ or Objective-C++.
std::chrono ought to be supported in g++ 4.8.*. However, when I try to compile using it using g++ 4.8.3, it cannot find various declarations. I am, of course, using -std=c++11.
For example this invocation (from an autogenerated file; that's why the -std appears twice):
g++-4.8 -g -msse2 -m64 <defines> <warnings> -std=c++11 -fexceptions -std=c++11 <includes'-path> -c <source-file.cpp> -o <out-path>
Produces this error:
<source-file, line>: error: ‘std::chrono::monotonic_clock’ has not been declared
I wasn't able to find very much that wasn't immediately a compiler version or missing -std=c++11. By inference from this, I shouldn't need anything else.
Question: what's wrong, how do I fix it?
There is no std::chrono::monotonic_clock in standard C++. There is a std::chrono::steady_clock, however.
In fairness to Microsoft - and burritos everywhere - there was a monotonic_clock in the working drafts during the development of C++11 which was replaced by steady_clock.
It seems to me that you could use code like this to determine whether you're using an old library implementation (that provides monotonic_clock but not steady_clock) or a new one (that provides steady_clock but possibly not monotonic_clock).
#if defined(__GLIBCXX__) && (__GLIBCXX__ < 20120322)
typedef std::chrono::monotonic_clock steady_clock;
#else
typedef std::chrono::steady_clock steady_clock;
#endif
The datestamp above corresponds to the libstdc++ shipped with GCC 4.7.0, according to GNU. I'd welcome any improvements or corrections to this code, for example to support libraries other than libstdc++.
I can't even get the basic codecvt example from cppreference.com to compile on GCC 4.9 or Clang 3.4, e.g.:
http://goo.gl/HZ5GLH
http://coliru.stacked-crooked.com/a/345d6d89949ac1e6
According to libstdc++ manual, part 22.4.1, it is missing the support for codecvt, even on the latest version.
And libc++ has complete support for C++11 and C++14 features, so you should use it on CLang, specifying the -stdlib=libc++ compiler flag (make sure you have it installed).
Edit: As of current versions of libstdc++, codecvt is now supported.