goto-instrument: handling of VarArgs

[stahlbauer]

It would be great if goto-instrument would be able to handle variable arguments and dump valid C code; example of a program that is not yet fully covered by the implementation:

#include<stdarg.h>
#include<stdlib.h>

void bb_verror_msg(const char *s, va_list p, const char *strerr) {
}

void bb_error_msg(const char *s, ...)
{
    va_list p;
    va_start(p, s);
    bb_verror_msg(s, p, NULL);
    va_end(p);
}

int main() {
    bb_error_msg("FOOO");
    return 0;
}

GCC complains about when parsing the file that was produced by goto-instrument:

error: cast specifies array type
   va_list p=(va_list)&s;
             ^
error: cast specifies array type
   p = ((va_list)NULL);

clang states that:

error: used type 'va_list' (aka
      '__builtin_va_list') where arithmetic or pointer type is
      required
  va_list p=(va_list)&s;
            ^        ~~
error: used type 'va_list' (aka
      '__builtin_va_list') where arithmetic or pointer type is
      required
  p = ((va_list)((void*)0));

[stahlbauer]

@tautschnig FYI

[stahlbauer]

A workaround would be a feature that abstracts away (declare them as extern) the definitions of some functions. For example, functions with variable argument list.

[stahlbauer]

The hackiest and ugliest solution I can imagine would be something like:

os_body << "// " << symbol.name << std::endl;
os_body << "// " << symbol.location << std::endl;
const std::string &fn_decl_str = make_decl(symbol.name, symbol.type);
if (fn_decl_str.find("...")==std::string::npos
    && fn_decl_str.find("va_list")==std::string::npos) {
  os_body<<fn_decl_str<<std::endl;
  os_body<<expr_to_string(b);
  os_body<<std::endl<<std::endl;
} else {
  if (fn_decl_str.find("extern ")==std::string::npos) {
    os_body<<"extern ";
  }
  os_body<<fn_decl_str<<";";
  os_body<<std::endl;
}

[stahlbauer]

The problem is still there. Functions with va_list parameters cause problems. For example, if the "va_list" gets assigned to a void** pointer.