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gcc_attribute.c revision 1.12 
      1 /*	$NetBSD: gcc_attribute.c,v 1.12 2022/08/25 19:03:48 rillig Exp $	*/
      2 # 3 "gcc_attribute.c"
      3 
      4 /*
      5  * Tests for the various attributes for functions, types, statements that are
      6  * provided by GCC.
      7  *
      8  * https://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html
      9  */
     10 
     11 void __attribute__((noinline))
     12 do_not_inline(void)
     13 {
     14 }
     15 
     16 /* All pointer arguments must be nonnull. */
     17 void __attribute__((nonnull))
     18 function_nonnull(void *, const void *, int);
     19 
     20 /*
     21  * The documentation suggests that the argument list of nonnull be nonempty,
     22  * but GCC 9.3.0 accepts an empty list as well, treating all parameters as
     23  * nonnull.
     24  */
     25 void __attribute__((nonnull()))
     26 function_nonnull_list(void *, const void *, int);
     27 
     28 /* Arguments 1 and 2 must be nonnull. */
     29 void __attribute__((nonnull(1, 2)))
     30 function_nonnull_list(void *, const void *, int);
     31 
     32 /*
     33  * Unknown attributes are skipped, as lint does not have a list of all known
     34  * GCC attributes.
     35  */
     36 void __attribute__((unknown_attribute))
     37 function_with_unknown_attribute(void);
     38 
     39 /*
     40  * There is an attribute called 'pcs', but that attribute must not prevent an
     41  * ordinary variable from being named the same.  Starting with scan.l 1.77
     42  * from 2017-01-07, that variable name generated a syntax error.  Fixed in
     43  * lex.c 1.33 from 2021-05-03.
     44  *
     45  * Seen in yds.c, function yds_allocate_slots.
     46  */
     47 int
     48 local_variable_pcs(void)
     49 {
     50 	int pcs = 3;
     51 	return pcs;
     52 }
     53 
     54 /*
     55  * FIXME: The attributes are handled by different grammar rules even though
     56  *  they occur in the same syntactical position.
     57  *
     58  * Grammar rule abstract_decl_param_list handles the first attribute.
     59  *
     60  * Grammar rule direct_abstract_declarator handles all remaining attributes.
     61  *
     62  * Since abstract_decl_param_list contains type_attribute_opt, this could be
     63  * the source of the many shift/reduce conflicts in the grammar.
     64  */
     65 int
     66 func(
     67     int(int)
     68     __attribute__((__noreturn__))
     69     __attribute__((__noreturn__))
     70 );
     71 
     72 /*
     73  * https://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html says that the
     74  * attribute-list is a "possibly empty comma-separated sequence of
     75  * attributes".
     76  *
     77  * No matter whether this particular example is interpreted as an empty list
     78  * or a list containing a single empty attribute, the result is the same in
     79  * both cases.
     80  */
     81 void one_empty_attribute(void)
     82     __attribute__((/* none */));
     83 
     84 /*
     85  * https://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html further says that
     86  * each individual attribute may be "Empty. Empty attributes are ignored".
     87  */
     88 void two_empty_attributes(void)
     89     __attribute__((/* none */, /* still none */));
     90 
     91 /*
     92  * Ensure that __attribute__ can be specified everywhere in a declaration.
     93  * This is the simplest possible requirement that covers all valid code.
     94  * It accepts invalid code as well, but these cases are covered by GCC and
     95  * Clang already.
     96  *
     97  * Since lint only parses the attributes but doesn't really relate them to
     98  * identifiers or other entities, ensuring that valid code can be parsed is
     99  * enough for now.
    100  *
    101  * To really associate __attribute__ with the corresponding entity, the
    102  * grammar needs to be rewritten, see the example with __noreturn__ above.
    103  */
    104 __attribute__((deprecated("d1")))
    105 const
    106 __attribute__((deprecated("d2")))
    107 int
    108 __attribute__((deprecated("d3")))
    109 *
    110 // The below line would produce a syntax error.
    111 // __attribute__((deprecated("d3")))
    112 const
    113 __attribute__((deprecated("d4")))
    114 identifier
    115 __attribute__((deprecated("d5")))
    116 (
    117     __attribute__((deprecated("d6")))
    118     void
    119     __attribute__((deprecated("d7")))
    120     )
    121     __attribute__((deprecated("d8")))
    122 ;
    123 
    124 /*
    125  * The attribute 'const' provides stronger guarantees than 'pure', and
    126  * 'volatile' is not defined.  To keep the grammar simple, any T_QUAL is
    127  * allowed at this point, but only syntactically.
    128  */
    129 int const_function(int) __attribute__((const));
    130 /* cover 'gcc_attribute_spec: T_QUAL' */
    131 /* expect+1: error: syntax error 'volatile' [249] */
    132 int volatile_function(int) __attribute__((volatile));
    133