8.2 ANSI-Compliance

The latest publically available version of the standard ISO/IEC 9899 - Programming languages - C should be available at: http://www.open-std.org/jtc1/sc22/wg14/www/standards.html#9899.

Deviations from the compliance:

• functions are not reentrant unless explicitly declared as such or the --stack-auto command line option is specified.
• structures and unions cannot be assigned values directly, cannot be passed as function parameters or assigned to each other and cannot be a return value from a function, e.g.:

  struct s { ... };  
  struct s s1, s2;  
  foo()  
  {  
      ...  
      s1 = s2 ; /* is invalid in SDCC although allowed in ANSI */  
      ...  
  } 
  struct s foo1 (struct s parms) /* invalid in SDCC although allowed in ANSI */ 
  {  
      struct s rets;  
      ...  
      return rets; /* is invalid in SDCC although allowed in ANSI */  
  }

• initialization of structure arrays must be fully braced.

  struct s { char x } a[] = {1, 2};     /* invalid in SDCC */ 
  struct s { char x } a[] = {{1}, {2}}; /* OK */

• 'long long' (64 bit integers) not supported.
• 'double' precision floating point not supported.
• Old K&R style function declarations are NOT allowed.

  foo(i,j) /* this old style of function declarations */  
  int i,j; /* is valid in ANSI but not valid in SDCC */  
  {  
      ...  
  }

• Most enhancements in C99 are not supported, e.g.:

  for (int i=0; i<10; i++) /* is invalid in SDCC although allowed in C99 */

• But some have been added recently in SDCC 2.7.0. They must be considered alpha quality however.

  inline int increment (int a) { return a+1; } /* inlines the increment without function call overhead */ 
  int * restrict p; /* accepted but ignored */

• Certain words that are valid identifiers in the standard may be reserved words in SDCC unless the --std-c89 or --std-c99 command line options are used. These may include (depending on the selected processor): 'at', 'banked', 'bit', 'code', 'critical', 'data', 'eeprom', 'far', 'flash', 'idata', 'interrupt', 'near', 'nonbanked', 'pdata', 'reentrant', 'sbit', 'sfr', 'shadowregs', 'sram', 'using', 'wparam', 'xdata', '_overlay', '_asm', '_endasm', and '_naked'. Compliant equivalents of these keywords are always available in a form that begin with two underscores, f.e. '__data' instead of 'data'.
• Integer promotion of variable arguments is not performed if the argument is explicitly taypecasted unless the --std-c89 or --std-c99 command line options are used.

  void vararg_func (char *str, ...) { str; } 
   
  void main (void) 
  { 
    char c = 10; 
   
    /* argument u is promoted to int before 
     * passing to function */ 
    vararg_func ("%c", c); 
   
    /* argument u is not promoted to int, 
     * it is passed as char to function 
     * if -std-cXX is not defined; 
     * is promoted to int before passing 
     * to function if -std-cXX is defined */ 
    vararg_func ("%bc", (char)u); 
  }