Sun CC compiler generates warnings about linkage

[svigerske]

Issue created by migration from Trac.

Original creator: @mjsaltzman

Original creation time: 2006-10-04 15:58:18

Assignee: somebody

Version:

During a make of CLP using the Solaris CC compiler (CC: Sun C++ 5.7 2005/01/07), the following warnings are generated:

/bin/bash ../libtool --tag=CXX --mode=compile CC -DHAVE_CONFIG_H  -I. -I`echo .` -I../inc      -O4  -DNDEBUG -c -o CoinModelUseful2.lo CoinModelUseful2.cpp
 CC -DHAVE_CONFIG_H -I. -I. -I../inc -O4 -DNDEBUG -c CoinModelUseful2.cpp  -KPIC -DPIC -o .libs/CoinModelUseful2.o
"CoinModelUseful2.cpp", line 764: Warning (Anachronism): Using extern "C" double(*)(double) to initialize double(*const)(double).
"CoinModelUseful2.cpp", line 765: Warning (Anachronism): Using extern "C" double(*)(double) to initialize double(*const)(double).
"CoinModelUseful2.cpp", line 766: Warning (Anachronism): Using extern "C" double(*)(double) to initialize double(*const)(double).
"CoinModelUseful2.cpp", line 767: Warning (Anachronism): Using extern "C" double(*)(double) to initialize double(*const)(double).
"CoinModelUseful2.cpp", line 768: Warning (Anachronism): Using extern "C" double(*)(double) to initialize double(*const)(double).
"CoinModelUseful2.cpp", line 769: Warning (Anachronism): Using extern "C" double(*)(double) to initialize double(*const)(double).
"CoinModelUseful2.cpp", line 770: Warning (Anachronism): Using extern "C" double(*)(double) to initialize double(*const)(double).
"CoinModelUseful2.cpp", line 771: Warning (Anachronism): Using extern "C" double(*)(double) to initialize double(*const)(double).
8 Warning(s) detected.

The offending lines in CoinModelUseful2.cpp are:

     struct init
     {
       char const *fname;
       double (*fnct) (double);
     };
     
     struct init const arith_fncts[] =
     {
       {"sin",  sin},
       {"cos",  cos},
       {"atan", atan},
       {"ln",   log},
       {"exp",  exp},
       {"sqrt", sqrt},
       {"fabs", fabs},
       {"abs", fabs},
       {NULL, 0}
     };

See the discussion here: http://docs.sun.com/source/819-3689/Ch3.Std.html, Section 3.11.
The problem is that the standard C library functions are declared with "C" linkage in the Sun libraries. The "anachronism" and the fact that they are warnings stem from the fact that "C" and "C++" linkage are binary-compatible in the Sun libs, but (a) they need not be (in which case, things are likely to break), and (b) the C++ standard permits standard C lib functions to have either "C" or "C++" linkage.

The warning can be eliminated in this case by enclosing the declaration of struct init in
extern "C" {...} (and similarly enclosing the declaration of struct symrec in CoinModelUseful.hpp), but for systems where the standard C functions have C++ linkage, that won't work. I can't think of a completely portable way to handle this other than to define in BuildTools a preprocessor symbol such as STD_C_FUNCTION_LINKAGE, which is defined to be C or C++ depending on the compiler and define the structs inside extern "STD_C_FUNCTION_LINKAGE" {...}. Even that's not quite ideal, as the structs could then only be used to hold pointers to standard C functions.

[svigerske]

Comment by ladanyi created at 2006-12-10 04:50:14

Will fix it later when we figure out how to do it properly. For now, let's live with the warnings...

--Laci

[svigerske]

Comment by ladanyi created at 2006-12-10 04:50:14

Changing assignee from somebody to ladanyi.

[svigerske]

Comment by ladanyi created at 2006-12-10 04:50:14

Changing status from new to assigned.

[svigerske]

The offending code had been changed to

struct init {
  char const *fname;
  double (*fnct)(double);
};

inline double sin_wrapper(double x) { return sin(x); }
inline double cos_wrapper(double x) { return cos(x); }
inline double atan_wrapper(double x) { return atan(x); }
inline double log_wrapper(double x) { return log(x); }
inline double exp_wrapper(double x) { return exp(x); }
inline double sqrt_wrapper(double x) { return sqrt(x); }
inline double fabs_wrapper(double x) { return fabs(x); }
inline double floor_wrapper(double x) { return floor(x); }
inline double ceil_wrapper(double x) { return ceil(x); }

struct init const arith_fncts[] = {
  { "sin", sin_wrapper },
  { "cos", cos_wrapper },
  { "atan", atan_wrapper },
  { "ln", log_wrapper },
  { "exp", exp_wrapper },
  { "sqrt", sqrt_wrapper },
  { "fabs", fabs_wrapper },
  { "abs", fabs_wrapper },
  { "floor", floor_wrapper },
  { "ceil", ceil_wrapper },
  { NULL, 0 }
};

in f209c9b (BSP 12 years ago).

I'll assume that this fixed the issue. Please reopen if you can still reproduce with current code.