[boost] [program_options] compile error in libs/program_options/src/convert.cpp

From: Glenn Schrader (gschrad_at_[hidden])
Date: 2007-01-09 12:39:11

I get the following error while compiling 
libs/program_options/src/convert.cpp.

libs/program_options/src/convert.cpp:100:   instantiated from here
libs/program_options/src/convert.cpp:48: warning: missing braces around 
initializer for 'int [6]'

Line 48 is:

  std::mbstate_t state = {0};

The problem is simple but wasn't immediately obvious. The definition of 
mbstate_t from the cwchar header is:

  typedef struct
  {
    int __fill[6];
  } mbstate_t;

The int[6] in the error message is actually coming from the first 
element in mbstate_t. A change that makes the error go away is:

  std::mbstate_t state = {{0}};

Since I found cwchar in the include/c++/4.1.1 directory the layout of 
this structure probably isn't guaranteed to be the same across compilers 
or compiler versions. Perhaps the following would be better:

  std::mbstate_t state;
  memset( &state, 0, sizeof(state) );

Has anybody noticed whether this structure has the same definition 
across compilers? (i.e. gcc, VC, SunCC, etc)

-glenn