I currently use C++ string properties and specifically its pop_back() fonction. As written in the title, it leads to an error (same error seen ini an other topic) :
‘std::string’ has no member named ‘pop_back’
But what's strange is that I already use C++11 specific properties (as "auto" for iterators, etc.) and I never get any error.
For information, I build my code under Ubuntu 12.04 with gcc 4.6.3. For me, this version is good enough. I also put "-std=c++0x" flag so I really don't know where is the point ?!
Moreover, I've seen, in previous topic, that it's better to use "-std=c++11" flag now. But when I try this, the following error appears :
unrecognized command line option ‘-std=c++11’
On gcc 4.6 (which had only partial support for the new standard) the option is -std=c++0x because at that time the release date (i.e., 2011) was still unknown.
Related
While trying to compile a simple range based for loop on MacOS Big Sur, I got this warning:
warning: range-based for loop is a C++11 extension [-Wc++11-extensions]
I tried using clang++ and g++ but both gave the same warning. Is there a way to always compile with C++11 without having to use -std=c++11 and without using aliases?
Edit: The reason I would prefer not to use -std=c++11 is because I want the compiler to default to C++11 or higher.
To provide this question with a proper answer, based on the discussion in the comments:
Compilers such as GCC and Clang set the default in their source code and it cannot be changed by, e.g., modifying a config file. The only way to change the default would be to change it in the source code and to compile the compiler yourself. This is not worth it.
Furthermore, compilers change their default language from time to time, and setting another default, e.g. to C++11, will make all non-C++11 code require setting the language version explicitly.
Here's the key point: code and compilation options belong together. Do not rely on compiler defaults. Any serious project will use a build system (e.g. Make) which specifies how to compile the project.
Edit
For completeness sake, the default C++ version for GCC 10.2.0 is hardcoded in /gcc/c-family/c-opts.c:
/* Set C++ standard to C++17 if not specified on the command line. */
if (c_dialect_cxx ())
set_std_cxx17 (/*ISO*/false);
The error that is being generated is below.
error: 'size' was not declared in this scope
When I use nums.size(), it is working fine. It could be because of using an older compiler version, but in my system when I check the version it shows 10.3.0, which I think is the latest version. How do I fix this?
The std::size function was added in C++17, therefore, you need to enable its support. With GCC, just add -std=c++17 as a command-line argument to your g++ call.
You can also check the libstdc++ source code: https://github.com/gcc-mirror/gcc/blob/master/libstdc%2B%2B-v3/include/bits/range_access.h#L236. As you can see, there is an #ifdef that makes std::size available only if C++17 (or higher standard) support is applied.
Within my bazel.rc file for the C++ Bazel build options, I have specified:
'build --cxxopt="-std=c++1y"'
When I try to change to build --cxxopt="-std=c++14", bazel Throws error of :
''build --cxxopt="-std=c++14"' is not an option'
, with a cursor below 4 in c++14. If I change the 4 to y (c++1y), it compiles with no problem. I tried adding 'std:make_unique' in my code (c++14 addition) , and it clearly does not compile (make _unique is not part of std) which is assume is complaining that c++14 is not set as the standard, hence no make_unique for me.
What is the latest supported version of C++ in bazel? More specifically, how do I enable C++14 / C++17 (and even C++2x) for Bazel build, it those are supported? Thanks!
NOTE: this is not the same as How to set C++ standard version when build with Bazel??. (I am not asking about cpp 11 and I am asking about a very specific toolchain -- GCC/g++) I am not using any of the tools suggested by that thread. I am using GCC / g++ and am restricted in not being able to use the tools suggested by the answer in the previous question, I've RTFMd and googled. Thanks in advance.
I am using SublimeLinter-clang with Sublime 3 to lint C++ code on MacOS Mojave. I am getting warnings and errors for code from later versions of C++. How do I set the default linting version to C++17?
For instance, I have the line:
auto game = SpinOut{};
and the editor marks the following:
1 warning: clang++ - 'auto' type specifier is a C++11 extension [-Wc++11-extensions]
clang++: error - expected '(' for function-style cast or type construction
I tried following the answer to this question but nothing changed. Below is my SublimeLinter.sublime.settings, and I still get the same error and warning.
SublimeLinter-clang is now maintained at https://github.com/SublimeLinter/SublimeLinter-clang rather than https://github.com/nirm03/SublimeLinter-clang.
In the newer version there was a pull request in 2018 that added support that gives users the ability to have different settings for the c linter and c++ linter. So the answer from 2017 in https://stackoverflow.com/a/42818098/17034 is currently outdated.
So it looks like you will need to change clang to clang++. It also looks like they changed extra_flags to args in the settings, so you will need to override the default args and add -std=c++11.
"linters":
{
"clang++": {
"args": "-Wall -fsyntax-only -fno-caret-diagnostics -std=c++11"
}
},
So in my CSE course we are given a header file to use right now for our programs that we're writing.
Unfortunately I can't get terminal to compile using that header, it gives quite a few errors (compiling with just 'g++'). Also, when I'm at my university and I'm using PuTTY I get the same errors while using this header. However, I don't get the errors when I compile with 'g++ -std=c++14'.
I've tried compiling with this command on terminal on my mac, but it says it doesn't recognize the c++14 part.
dhcp-10-202-147-243:hw1pr1 Admin$ g++ -std=c++14 hw1pr1.cpp
error: invalid value 'c++14' in '-std=c++14'
Any help on how I could get this to work would be greatly appreciated. Hopefully this all made some sort of sense.
Here's the error I get when I compile with the header file I'm talking about in terminal with just g++.
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/ext/hash_map:212:5: warning:
Use of the header <ext/hash_map> is deprecated. Migrate to <unordered_map>
[-W#warnings]
# warning Use of the header <ext/hash_map> is deprecated. Migrate to ...
^
In file included from read_first_name.cpp:1:
./std_lib_facilities_4.h:43:20: error: no matching function for call to object
of type 'hash<char *>'
return hash<char*>()(s.c_str());
^~~~~~~~~~~~~
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/ext/__hash:39:12: note:
candidate function not viable: 1st argument ('const value_type *'
(aka 'const char *')) would lose const qualifier
size_t operator()(char *__c) const _NOEXCEPT
^
In file included from read_first_name.cpp:1:
./std_lib_facilities_4.h:112:8: warning: comparison of unsigned expression < 0
is always false [-Wtautological-compare]
if (i<0||size()<=i) throw Range_error(i);
~^~
./std_lib_facilities_4.h:118:8: warning: comparison of unsigned expression < 0
is always false [-Wtautological-compare]
if (i<0||size()<=i) throw Range_error(i);
~^~
3 warnings and 1 error generated.
This error doesn't happen and the program will compile fully when I use PuTTY and 'g++ std=c++14'
There's lots of change between C++ standards, so what is valid in one revision need not be in another.
g++ defaults to -std=gnu++98 for C++, which is the decades old C++98-standard enhanced with GNU extensions (most of which are conformant).
Choose the proper revision: -std=c++1y -pedantic is a very close approximation to C++14.
What changes introduced in C++14 can potentially break a program written in C++11?
Looking at what you say you're having to use and the name format of that .cpp file, I think I'm in the same class. A year later, looks like, but here's my solution for archive's sake:
The std_lib_facilities.h header comes with the Bjarne Stroustrup textbook, "Programming: Principles and Practices Using C++". For those unaware, Bjarne Stroustrup invented C++ (he has a pretty good idea what he's talking about). Incidentally, the book is a fantastic way to learn C++, if one takes the time to actually read it. The std_lib_facilities.h header is just a convenient header file for beginners in C++, containing links to all the major standard libraries used in the textbook, as well as some helper functions that help account for potential mistakes or errors, or are just convenient for learning (such as an error() function that handles simple exception throwing for the student, or adding an "out of bounds" check for vectors). It's ultimately just a way to allow students to hop right into code without having to learn specifics about the header.
Stroustrup keeps updated with C++ and thus includes several libraries that require the c++11 standard. The CSCE department wants its students (at least in this early class) to connect to the department's Unix system and compile from there, in order to avoid confusion with downloading and updating compilers.
I happened to already have had a couple C++ classes beforehand, and thus already had g++ set up on my Ubuntu laptop. I avoided including the std_lib_facilities for as long as possible since I was getting the same error as Topic Creator Joe, where g++ didn't recognize the "c++11" part (manually including the required libraries worked fine until we had to use a class from the textbook that used one of the header's helper functions) . Eventually, I found a help topic online that advised me simply to update my g++ compiler to 4.7 or higher, since 4.6 and lower doesn't have support for C++11 (or, of course, C++14). It was oddly rather involved compared to updates one might be used to on Mac or Windows, and I doubt the exact process would apply, but that is (was?) likely the problem: it's just an older version of g++, and it needs an update to compile C++11 and later. I recommend searching for ways to update g++/gcc for Mac.
Should, y'know, anyone else with this problem stumble upon this and not have their problem solved yet.