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Re: [Mingw-users] Does MinGW not support -std=c++11 flag?

On Thu, Oct 13, 2016 at 5:14 PM, Keith Marshall <keithmarshall@xxxxxxxxxxxxxxxxxxxxx> wrote:

I've now published a mingwrt-3.22.3 patch release to address this
issue.  It should be installable via mingw-get, once the mirrors have
caught up with the catalogue updates; you will need to update your
local copy of the catalogue, before performing the installation, or
package upgrade.

- --

Thanks Keith,

That patch fixes the aforementioned issues with off_t and _fsize_t.

However there are some other errors when compiling allegro programs with the C++11 standard I mentioned before. I've narrowed down the cause to #including <string.h> before #including <string>, as was happening with my library. It causes all the undefined function errors listed below. It can be fixed by including <string> *before* <string.h> or compiling as gnu++11.

Trying to compile this simple example program with the following command (mingw32-g++ -Wall -O0 -std=c++11 -o mt.exe mt.cpp) causes the errors to appear :

#include <string.h>
#include <string>

int main(int argc , char** argv) {
   return 0;

The errors are as listed :

||=== Build: Release in Allegro5_backend (compiler: GNU GCC Compiler) ===|
c:\mingw\lib\gcc\mingw32\5.3.0\include\c++\cwchar|177|error: '::wcscat' has not been declared|
c:\mingw\lib\gcc\mingw32\5.3.0\include\c++\cwchar|178|error: '::wcscmp' has not been declared|
c:\mingw\lib\gcc\mingw32\5.3.0\include\c++\cwchar|179|error: '::wcscoll' has not been declared|
c:\mingw\lib\gcc\mingw32\5.3.0\include\c++\cwchar|180|error: '::wcscpy' has not been declared|
c:\mingw\lib\gcc\mingw32\5.3.0\include\c++\cwchar|181|error: '::wcscspn' has not been declared|
c:\mingw\lib\gcc\mingw32\5.3.0\include\c++\cwchar|183|error: '::wcslen' has not been declared|
c:\mingw\lib\gcc\mingw32\5.3.0\include\c++\cwchar|184|error: '::wcsncat' has not been declared|
c:\mingw\lib\gcc\mingw32\5.3.0\include\c++\cwchar|185|error: '::wcsncmp' has not been declared|
c:\mingw\lib\gcc\mingw32\5.3.0\include\c++\cwchar|186|error: '::wcsncpy' has not been declared|
c:\mingw\lib\gcc\mingw32\5.3.0\include\c++\cwchar|188|error: '::wcsspn' has not been declared|
c:\mingw\lib\gcc\mingw32\5.3.0\include\c++\cwchar|193|error: '::wcstok' has not been declared|
c:\mingw\lib\gcc\mingw32\5.3.0\include\c++\cwchar|196|error: '::wcsxfrm' has not been declared|
c:\mingw\lib\gcc\mingw32\5.3.0\include\c++\cwchar|204|error: '::wcschr' has not been declared|
c:\mingw\lib\gcc\mingw32\5.3.0\include\c++\cwchar|205|error: '::wcspbrk' has not been declared|
c:\mingw\lib\gcc\mingw32\5.3.0\include\c++\cwchar|206|error: '::wcsrchr' has not been declared|
c:\mingw\lib\gcc\mingw32\5.3.0\include\c++\cwchar|207|error: '::wcsstr' has not been declared|
c:\mingw\lib\gcc\mingw32\5.3.0\include\c++\cwchar||In function 'wchar_t* std::wcschr(wchar_t*, wchar_t)':|
c:\mingw\lib\gcc\mingw32\5.3.0\include\c++\cwchar|213|error: invalid conversion from 'const wchar_t*' to 'wchar_t*' [-fpermissive]|
c:\mingw\lib\gcc\mingw32\5.3.0\include\c++\cwchar|212|note:   initializing argument 1 of 'wchar_t* std::wcschr(wchar_t*, wchar_t)'|
c:\mingw\lib\gcc\mingw32\5.3.0\include\c++\cwchar||In function 'wchar_t* std::wcspbrk(wchar_t*, const wchar_t*)':|
c:\mingw\lib\gcc\mingw32\5.3.0\include\c++\cwchar|217|error: invalid conversion from 'const wchar_t*' to 'wchar_t*' [-fpermissive]|
c:\mingw\lib\gcc\mingw32\5.3.0\include\c++\cwchar|216|note:   initializing argument 1 of 'wchar_t* std::wcspbrk(wchar_t*, const wchar_t*)'|
c:\mingw\lib\gcc\mingw32\5.3.0\include\c++\cwchar||In function 'wchar_t* std::wcsrchr(wchar_t*, wchar_t)':|
c:\mingw\lib\gcc\mingw32\5.3.0\include\c++\cwchar|221|error: invalid conversion from 'const wchar_t*' to 'wchar_t*' [-fpermissive]|
c:\mingw\lib\gcc\mingw32\5.3.0\include\c++\cwchar|220|note:   initializing argument 1 of 'wchar_t* std::wcsrchr(wchar_t*, wchar_t)'|
c:\mingw\lib\gcc\mingw32\5.3.0\include\c++\cwchar||In function 'wchar_t* std::wcsstr(wchar_t*, const wchar_t*)':|
c:\mingw\lib\gcc\mingw32\5.3.0\include\c++\cwchar|225|error: invalid conversion from 'const wchar_t*' to 'wchar_t*' [-fpermissive]|
c:\mingw\lib\gcc\mingw32\5.3.0\include\c++\cwchar|224|note:   initializing argument 1 of 'wchar_t* std::wcsstr(wchar_t*, const wchar_t*)'|
c:\mingw\lib\gcc\mingw32\5.3.0\include\c++\bits\char_traits.h|358|error: 'wcslen' was not declared in this scope|
||=== Build finished: 21 error(s), 0 warning(s) (0 minute(s), 1 second(s)) ===|

I haven't had time to determine the exact cause of this, but I hoped it would be enough to give you to go on in order to make a fix. It also happens if you include <cstring> before <string>.

Marc D.
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