The "not", "and", etc... are keywords in C++ (macros in C). Is there any way to "enable" them in Visual Studio 2013? I'm able to use the words as macroses with iso646.h included. But VS seems not be able to recognize them as keywords.
Using /Za seems to enable them without including iso646.h, see it live, the following program produces an error without using /Za but works fine otherwise:
int main()
{
int x = 1, y = 0 ;
if (x and y)
{
//...
}
return 0;
}
As ta.speot.is indicates /Za disables extensions, the following documentation indicates you must include ios646.h otherwise:
Under /Ze, you have to include iso646.h if you want to use text forms of the following operators:
and it lists the alternative tokens below.
Note, I knew I saw this before, I include a link to a bug report for this in my answer to a similar question. Although this does not include the workaround noted above.
Note 2: Cheers and hth. - Alf indicates that there may be many undesirable consequences to turning off extension and therefore you may be better off just including iso646.h.
Use a forced include (option /FI) of the iso646.h header.
For work in the command interpreter you can put this in your CL environment variable, or e.g. in a response file.
Turning off Visual C++ language extensions with /Za can also do the trick, at the cost of rendering the compiler pretty much useless – since Microsoft code such as the Windows API headers generally uses the extensions.
On a more recent version of VS (tested on Version 15.7.0 Preview 3.0); ensure that conformance mode is set for visual studio:
It then compiles with the alternative operator representations.
Related
I try to run codes like
#include <string>
#include <iostream>
int main() {
std::string str = "This is a string";
std::cout << str.starts_with("name");
}
But intellisense will give out an error
"std::__cxx11::basic_string<char, std::char_traits,
std::allocator>" has no member "starts_with" C/C++(135) [6,9]
And It still can be build and produce a correct result.
Also it can find implementation in header file.
But the macro __cplusplus is defined as 201703L
I've already added a command -std=c++20 when building, why this happened?
Compiler: minGW 11.2 compiled by msys2
Assuming you are using Microsoft's C/C++ extension, you must configure the extension to use C++ 20 standard for intellisense.
The easiest way to do this is to add the line "C_Cpp.default.cppStandard": "c++20" to your settings.json file. You can also find the setting in the GUI under the name "Cpp Standard". Selecting c++20 from its dropdown will achieve the same result.
Note that this setting is, by default, set as a global user defaults. You can configure it per-workspace by selecting the Workspace tab in the settings GUI and changing that Cpp Standard dropdown to c++20.
As for why adding the -std=c++20 flag didn't work: -std=c++20 just tells your compiler which standard to use to build your code. 'Intellisense' does not receive this flag because it is a separate tool from the compiler and is therefore not required to support all the standards the compiler supports. It may support less even, although Intellisense tools usually support as current a standard as possible. Therefore the language standard for Intellisense must be configured separately from the compiler (in this case).
Final Note: After changing the setting, try closing and re-opening VS Code. In my experience changing the language standard setting can cause some weirdness to happen. Closing and re-opening VS Code seems to ensure the setting changes take full effect.
When browsing the source of the open source .NET Framework 4.7 I stumbled across the C++ header sal.h and found a line of code saying [source_annotation_attribute( SA( Method ) )] which seems to be similar to attributes and the AttributesUsage class in C#.
Now I know that generally, there are no user defined attributes in C++ as there are in C#, and my first guess was that [source_annotation_attribute( SA( Method ) )] is just a macro, but it is neither defined in sal.h nor in any other headers, since sal.h does not #include any.
My next guess is that [source_annotation_attribute] is actually built in the MSVC, just like for e.g. [[noreturn]] attribute.
I would be glad if somebody could shed some light on what it actually is and if I can declare my own attributes similar to that, if it is not built into the compiler.
If you want to see for your self, the particular file is \Source\externalapis\legacy\vctools\vc12\inc\vc\sal.h and the attribute occurs (among others) in line 1934.
Here is an example on the usage in sal.h:
[source_annotation_attribute( SA( Method ) )]
struct __M_
{
#ifdef __cplusplus // [
__M_();
#endif // ]
int __d_;
};
typedef struct __M_ __M_;
Many thanks in advance.
To conclude what #VTT has already said, it looks like the source_annotation_attribute is a compiler inbuilt construct, which is shipped as part of a Microsoft extension to C++
(even if it is not mentioned there because it is an implementation detail, meant for internal use only) that is valid only when compiled with the compiler switch /Ze
What adds to this is the fact that Microsofts SAL is built in deeply in Visual Studio
i.e.
Build -> Run Code Analysis on Solution
and since Visual Studio (obviously) uses their MSVC compiler, it is not too implausible that Microsoft would not build any internal constructs like this in their compilers.
The "not", "and", etc... are keywords in C++ (macros in C). Is there any way to "enable" them in Visual Studio 2013? I'm able to use the words as macroses with iso646.h included. But VS seems not be able to recognize them as keywords.
Using /Za seems to enable them without including iso646.h, see it live, the following program produces an error without using /Za but works fine otherwise:
int main()
{
int x = 1, y = 0 ;
if (x and y)
{
//...
}
return 0;
}
As ta.speot.is indicates /Za disables extensions, the following documentation indicates you must include ios646.h otherwise:
Under /Ze, you have to include iso646.h if you want to use text forms of the following operators:
and it lists the alternative tokens below.
Note, I knew I saw this before, I include a link to a bug report for this in my answer to a similar question. Although this does not include the workaround noted above.
Note 2: Cheers and hth. - Alf indicates that there may be many undesirable consequences to turning off extension and therefore you may be better off just including iso646.h.
Use a forced include (option /FI) of the iso646.h header.
For work in the command interpreter you can put this in your CL environment variable, or e.g. in a response file.
Turning off Visual C++ language extensions with /Za can also do the trick, at the cost of rendering the compiler pretty much useless – since Microsoft code such as the Windows API headers generally uses the extensions.
On a more recent version of VS (tested on Version 15.7.0 Preview 3.0); ensure that conformance mode is set for visual studio:
It then compiles with the alternative operator representations.
I am a beginner was trying to do some C++ programming on Xcode. It works fine, but when I try to compile the same c++ file on my windows pc using VS, there were some errors. After I look at my code closely, there are really some stupid mistakes that I have made which caused the errors, but Xcode seemed to have ignored them...
My question is that is there any setting that I need to change to prevent Xcode from being so smart?
For example, the following code can actually compile in xcode:
#include <iostream>
using namespace std;
int main() {
if (true or false){
cout << "How is this possible? \n";
}
return 0;
}
There are also other cases where the code is actually wrong, but it can compile just fine is Xcode which is the annoying part and I want to disable that.
As far as I can see there is nothing wrong with your code.
The ISO C++ standard does not specify which standard headers are included by other standard headers. So, it is entirely possible that the version of iostream used by Xcode directly or indirectly includes ciso646. Whereas Visual Studio's version of iostream does not include ciso646. There are many similar cases with other headers. You just need to read the error messages and realize that your error (when you move your file to a different platform) is due to a missing header file.
It would be nice if writing portable code meant writing code in accordance with the C++ standard specification, but unfortunately that's not the case. Although there are various compiler options on various implementations which can help bring different implementations closer together, in general you will just have to bring the code into the target environment and actually test it there.
So ultimately writing portable code means you'll have to learn some subset of C++ that is accepted by all the implementations you want to target.
or is an 'alternative token' in C++, and VS is incorrect to reject it. There's no option in Xcode to disable support for alternative tokens. However VS has non-standard support for or as a macro using the header <ciso646>, and Xcode does have a header <ciso646> which does nothing (as the standard specifies). So you can write code which uses or and which works in both Xcode and VS by including this header.
#include <iostream>
#include <ciso646> // does nothing in Xcode, allows `or` in VS
using namespace std;
int main() {
if (true or false){
cout << "How is this possible? \n";
}
return 0;
}
Unfortunately VS can't support all of the alternative tokens through macros and so Xcode will still support some that VS doesn't.
There are also other cases where the code is actually wrong, but it can compile just fine is Xcode which is the annoying part and I want to disable that.
If you give specific examples then I can provide additional advice on how to write portable code.
Rather than changing your Xcode settings, I suggest cross-checking your code using another development environment.
If you're looking for something cheap and full-proof. Download a VirtualBox Windows VM, and run download Dev C++ (bloodhshed)
VS does not support or: you need to use || instead.
You can include some special files but it doesn't inject or sufficiently well into the language for it to work in all instances.
If you want to suppress use of or (and your compiler supports no better way)
#define it to something that emits a compiler error, for example
#define or OR
This at least means that the nature of the compilation errors will be identical on Xcode and VC.
I can inhibit many warnings in Visual Studio 2005 SP1 in the C/C++ Advanced property page, which causes the IDE to use the /wd switch on the command line which invokes the compiler. However, when I try to inhibit warning 4200 (nonstandard extension used : zero-sized array in struct/union), it still appears when I compile. (Of course it's justified; I'm just not in a position to fix the code, nor would it be worth bothering, because it's generated, and the warning is entirely benign under the circumstances.) Does anybody happen to know if this is a bug in the compiler? Or might there be something I can do about it?
To completely disable the warning in the file you can add the following to the top of the file
#pragma warning(disable:2400)
If you want some more flexibility other than a blanket disable for the file, the following page lists several other more fine grained options.
http://msdn.microsoft.com/en-us/library/2c8f766e(VS.80).aspx
It's unclear based on your information as to whether or not it's a bug in the compiler or a configuration issue. I would lean towards a configuration issue, specifically conflicting compiler options that is making it difficult to suppress the warning.
EDIT
OP mentioned they can't control the generated code so they can't directly include the pragma. If that's the case then try this trick. Say the file name is Generated.cpp. No longer include Generated.cpp as one of the files to compile. Instead create a new file called Example.cpp with the following contents
#pragma warning(disable:2400)
#include "Generated.cpp"
Now you'll get the text of Generated.cpp with the disabled warning by only compiling Example.cpp.
You mean like with pragma?
#pragma warning( disable : 2400 )