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8.2 ANSI-Compliance

The latest publicly 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);`
  > `}`

Next: 8.3 Cyclomatic Complexity Up: 8. SDCC Technical Data Previous: 8.1.13 Peephole Optimizer Contents Index