MacOS compiler error on wcsnrtombs (UNICODE)

[pedro-vicente]

Environment

• nanodbc version: master branch
• DBMS name/version: unixODBC
• ODBC connection string:
• OS and Compiler:
• CMake settings:

Actual behavior

Expected behavior

Minimal Working Example

I get a compiler error building on MacOS

cmake .. -DNANODBC_ENABLE_UNICODE=ON

-- The CXX compiler identification is AppleClang 12.0.0.12000032
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /Library/Developer/CommandLineTools/usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- nanodbc version: 2.13.0
-- nanodbc compile: C++14
-- Performing Test CXX_SUPPORTS_STDLIB
-- Performing Test CXX_SUPPORTS_STDLIB - Success
-- nanodbc build: Disable linking libc++ - OFF
-- nanodbc feature: ODBC Version Override - OFF
-- nanodbc feature: Disable async features - OFF
-- nanodbc feature: Enable Unicode - ON
-- nanodbc feature: Enable Boost - OFF
-- nanodbc feature: Enable SQL_NO_DATA bug workaround - OFF
-- nanodbc build: ODBC on Unix - unixODBC
-- ODBC compile flags: -I/usr/local/Cellar/unixodbc/2.3.9/include
-- ODBC link flags: -L/usr/local/Cellar/unixodbc/2.3.9/lib -lodbc
-- Use rpaths on Mac OS X - ON
-- nanodbc build: Enable nanodbc target - STATIC
-- nanodbc build: Disable install target - OFF
-- nanodbc build: Disable tests target - OFF
-- nanodbc build: Disable examples target - OFF
-- Configuring done
-- Generating done
-- Build files have been written to: /Volumes/Home/pvn/dev/nanodbc/build

errors

make
Scanning dependencies of target nanodbc
[  3%] Building CXX object CMakeFiles/nanodbc.dir/nanodbc/nanodbc.cpp.o
[  6%] Linking CXX static library libnanodbc.a
[  6%] Built target nanodbc
Scanning dependencies of target vertica_tests
[ 10%] Building CXX object test/CMakeFiles/vertica_tests.dir/main.cpp.o
In file included from /Volumes/Home/pvn/dev/nanodbc/test/main.cpp:9:
/Volumes/Home/pvn/dev/nanodbc/test/base_test_fixture.h:62:5: error: no matching function for call to 'wcsnrtombs'
    wcsnrtombs(&out[0], &source, characters.size(), out.length(), nullptr);
    ^~~~~~~~~~
/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk/usr/include/wchar.h:203:9: note: candidate function not viable:
      no known conversion from 'std::__1::basic_string<char16_t, std::__1::char_traits<char16_t>,
      std::__1::allocator<char16_t> >::value_type *' (aka 'char16_t *') to 'char *' for 1st argument
size_t  wcsnrtombs(char * __restrict, const wchar_t ** __restrict, size_t,
        ^
In file included from /Volumes/Home/pvn/dev/nanodbc/test/main.cpp:9:
/Volumes/Home/pvn/dev/nanodbc/test/base_test_fixture.h:85:19: error: no matching function for call to 'mbsnrtowcs'
    size_t size = mbsnrtowcs(nullptr, in.data(), in.length(), 0, nullptr);
                  ^~~~~~~~~~
/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk/usr/include/wchar.h:195:9: note: candidate function not viable:
      no known conversion from 'const std::__1::basic_string<char16_t, std::__1::char_traits<char16_t>,
      std::__1::allocator<char16_t> >::value_type *' (aka 'const char16_t *') to 'const char **' for 2nd argument
size_t  mbsnrtowcs(wchar_t * __restrict, const char ** __restrict, size_t,
        ^
In file included from /Volumes/Home/pvn/dev/nanodbc/test/main.cpp:9:
/Volumes/Home/pvn/dev/nanodbc/test/base_test_fixture.h:89:17: error: cannot initialize a variable of type 'const char *'
      with an rvalue of type 'const std::__1::basic_string<char16_t, std::__1::char_traits<char16_t>,
      std::__1::allocator<char16_t> >::value_type *' (aka 'const char16_t *')
    const char* source = in.data();
                ^        ~~~~~~~~~

[pedro-vicente]

this is simply a nasty cast or conversion from std::string to char *
instead of trying to fix that, it seems that the generic fall trough case of

out = std::wstring_convert<std::codecvt_utf8_utf16<char16_t>, char16_t>().to_bytes(in);

can be used for the CLang compiler
so, a solution could be to let it fall to this case by changing from

#elif defined(__GNUC__) && __GNUC__ < 5 

to

#elif defined(__GNUC__) && __GNUC__ < 5 && !defined(__llvm__)

no errors in this case
except that the the odbc library was not found (unrelated to this)

ld: library not found for -lodbc

source

https://stackoverflow.com/questions/38499462/how-to-tell-clang-to-stop-pretending-to-be-other-compilers

[pedro-vicente]

to detect unixODBC I use this on my Cmake

if(UNIX)
  find_path(ODBC_INCLUDE sql.h ${find_opt})
  if(NOT ODBC_INCLUDE)
    message(FATAL_ERROR "sql.h header file not found")
  else()
    message("-- Found sql.h header file at: " ${ODBC_INCLUDE})
  endif()
  include_directories(${ODBC_INCLUDE})
  find_library(ODBC_LIBRARY NAMES odbc PATHS "/usr/local/lib")
  if(NOT ODBC_LIBRARY)
    message(FATAL_ERROR "ODBC library not found$")
  else()
    message("-- Found ODBC library at: " ${ODBC_LIBRARY})
  endif()
  set(lib_dep ${lib_dep} ${ODBC_LIBRARY})
endif()