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Diffstat (limited to 'contrib/gcc/doc/c-tree.texi')
| -rw-r--r-- | contrib/gcc/doc/c-tree.texi | 162 |
1 files changed, 91 insertions, 71 deletions
diff --git a/contrib/gcc/doc/c-tree.texi b/contrib/gcc/doc/c-tree.texi index fbc90fa3..d1afe65 100644 --- a/contrib/gcc/doc/c-tree.texi +++ b/contrib/gcc/doc/c-tree.texi @@ -1,4 +1,4 @@ -@c Copyright (c) 1999, 2000, 2001, 2002, 2003 Free Software Foundation, Inc. +@c Copyright (c) 1999, 2000, 2001, 2002, 2003, 2004 Free Software Foundation, Inc. @c Free Software Foundation, Inc. @c This is part of the GCC manual. @c For copying conditions, see the file gcc.texi. @@ -98,24 +98,24 @@ Many macros behave as predicates. Many, although not all, of these predicates end in @samp{_P}. Do not rely on the result type of these macros being of any particular type. You may, however, rely on the fact that the type can be compared to @code{0}, so that statements like -@example +@smallexample if (TEST_P (t) && !TEST_P (y)) x = 1; -@end example +@end smallexample @noindent and -@example +@smallexample int i = (TEST_P (t) != 0); -@end example +@end smallexample @noindent are legal. Macros that return @code{int} values now may be changed to return @code{tree} values, or other pointers in the future. Even those that continue to return @code{int} may return multiple nonzero codes where previously they returned only zero and one. Therefore, you should not write code like -@example +@smallexample if (TEST_P (t) == 1) -@end example +@end smallexample @noindent as this code is not guaranteed to work correctly in the future. @@ -124,7 +124,7 @@ functions described here. In particular, no guarantee is given that the values are lvalues. In general, the names of macros are all in uppercase, while the names of -functions are entirely in lower case. There are rare exceptions to this +functions are entirely in lowercase. There are rare exceptions to this rule. You should assume that any macro or function whose name is made up entirely of uppercase letters may evaluate its arguments more than once. You may assume that a macro or function whose name is made up @@ -555,11 +555,9 @@ This node is used to represent a type the knowledge of which is insufficient for a sound processing. @item OFFSET_TYPE -This node is used to represent a data member; for example a -pointer-to-data-member is represented by a @code{POINTER_TYPE} whose -@code{TREE_TYPE} is an @code{OFFSET_TYPE}. For a data member @code{X::m} -the @code{TYPE_OFFSET_BASETYPE} is @code{X} and the @code{TREE_TYPE} is -the type of @code{m}. +This node is used to represent a pointer-to-data member. For a data +member @code{X::m} the @code{TYPE_OFFSET_BASETYPE} is @code{X} and the +@code{TREE_TYPE} is the type of @code{m}. @item TYPENAME_TYPE Used to represent a construct of the form @code{typename T::A}. The @@ -790,7 +788,7 @@ This predicate holds whenever its argument represents a class-type with default constructor. @item CLASSTYPE_HAS_MUTABLE -@item TYPE_HAS_MUTABLE_P +@itemx TYPE_HAS_MUTABLE_P These predicates hold for a class-type having a mutable data member. @item CLASSTYPE_NON_POD_P @@ -873,15 +871,15 @@ This predicate holds if the declaration was implicitly generated by the compiler. For example, this predicate will hold of an implicitly declared member function, or of the @code{TYPE_DECL} implicitly generated for a class type. Recall that in C++ code like: -@example +@smallexample struct S @{@}; -@end example +@end smallexample @noindent is roughly equivalent to C code like: -@example +@smallexample struct S @{@}; typedef struct S S; -@end example +@end smallexample The implicitly generated @code{typedef} declaration is represented by a @code{TYPE_DECL} for which @code{DECL_ARTIFICIAL} holds. @@ -1021,34 +1019,35 @@ will always return the function itself, and @code{OVL_NEXT} will always be @code{NULL_TREE}. To determine the scope of a function, you can use the -@code{DECL_REAL_CONTEXT} macro. This macro will return the class +@code{DECL_CONTEXT} macro. This macro will return the class (either a @code{RECORD_TYPE} or a @code{UNION_TYPE}) or namespace (a @code{NAMESPACE_DECL}) of which the function is a member. For a virtual function, this macro returns the class in which the function was actually defined, not the base class in which the virtual declaration -occurred. If a friend function is defined in a class scope, the -@code{DECL_CLASS_CONTEXT} macro can be used to determine the class in +occurred. + +If a friend function is defined in a class scope, the +@code{DECL_FRIEND_CONTEXT} macro can be used to determine the class in which it was defined. For example, in -@example +@smallexample class C @{ friend void f() @{@} @}; -@end example -the @code{DECL_REAL_CONTEXT} for @code{f} will be the -@code{global_namespace}, but the @code{DECL_CLASS_CONTEXT} will be the +@end smallexample +@noindent +the @code{DECL_CONTEXT} for @code{f} will be the +@code{global_namespace}, but the @code{DECL_FRIEND_CONTEXT} will be the @code{RECORD_TYPE} for @code{C}. -The @code{DECL_REAL_CONTEXT} and @code{DECL_CLASS_CONTEXT} are not -available in C; instead you should simply use @code{DECL_CONTEXT}. In C, -the @code{DECL_CONTEXT} for a function maybe another function. This -representation indicates that the GNU nested function extension is in -use. For details on the semantics of nested functions, see the GCC -Manual. The nested function can refer to local variables in its +In C, the @code{DECL_CONTEXT} for a function maybe another function. +This representation indicates that the GNU nested function extension +is in use. For details on the semantics of nested functions, see the +GCC Manual. The nested function can refer to local variables in its containing function. Such references are not explicitly marked in the tree structure; back ends must look at the @code{DECL_CONTEXT} for the referenced @code{VAR_DECL}. If the @code{DECL_CONTEXT} for the referenced @code{VAR_DECL} is not the same as the function currently -being processed, and neither @code{DECL_EXTERNAL} nor @code{DECL_STATIC} -hold, then the reference is to a local variable in a containing -function, and the back end must take appropriate action. +being processed, and neither @code{DECL_EXTERNAL} nor +@code{DECL_STATIC} hold, then the reference is to a local variable in +a containing function, and the back end must take appropriate action. @menu * Function Basics:: Function names, linkage, and so forth. @@ -1379,7 +1378,7 @@ the expression has been omitted. A substatement may in fact be a list of statements, connected via their @code{TREE_CHAIN}s. So, you should always process the statement tree by looping over substatements, like this: -@example +@smallexample void process_stmt (stmt) tree stmt; @{ @@ -1398,7 +1397,7 @@ void process_stmt (stmt) stmt = TREE_CHAIN (stmt); @} @} -@end example +@end smallexample In other words, while the @code{then} clause of an @code{if} statement in C++ can be only one statement (although that one statement may be a compound statement), the intermediate representation will sometimes use @@ -1409,18 +1408,18 @@ several statements chained together. Used to represent an inline assembly statement. For an inline assembly statement like: -@example +@smallexample asm ("mov x, y"); -@end example +@end smallexample The @code{ASM_STRING} macro will return a @code{STRING_CST} node for @code{"mov x, y"}. If the original statement made use of the extended-assembly syntax, then @code{ASM_OUTPUTS}, @code{ASM_INPUTS}, and @code{ASM_CLOBBERS} will be the outputs, inputs, and clobbers for the statement, represented as @code{STRING_CST} nodes. The extended-assembly syntax looks like: -@example +@smallexample asm ("fsinx %1,%0" : "=f" (result) : "f" (angle)); -@end example +@end smallexample The first string is the @code{ASM_STRING}, containing the instruction template. The next two strings are the output and inputs, respectively; this statement has no clobbers. As this example indicates, ``plain'' @@ -1452,9 +1451,9 @@ the same type as the condition expression in the switch statement. Otherwise, if both @code{CASE_LOW} and @code{CASE_HIGH} are defined, the statement is a range of case labels. Such statements originate with the extension that allows users to write things of the form: -@example +@smallexample case 2 ... 5: -@end example +@end smallexample The first value will be @code{CASE_LOW}, while the second will be @code{CASE_HIGH}. @@ -1547,10 +1546,10 @@ This is used for branch prediction. Used to represent a C++ @code{catch} block. The @code{HANDLER_TYPE} is the type of exception that will be caught by this handler; it is -equal (by pointer equality) to @code{CATCH_ALL_TYPE} if this handler -is for all types. @code{HANDLER_PARMS} is the @code{DECL_STMT} for -the catch parameter, and @code{HANDLER_BODY} is the -@code{COMPOUND_STMT} for the block itself. +equal (by pointer equality) to @code{NULL} if this handler is for all +types. @code{HANDLER_PARMS} is the @code{DECL_STMT} for the catch +parameter, and @code{HANDLER_BODY} is the @code{COMPOUND_STMT} for the +block itself. @item IF_STMT @@ -1563,9 +1562,9 @@ evaluated, the statement should be executed. Then, the @code{TREE_VALUE} should be used as the conditional expression itself. This representation is used to handle C++ code like this: -@example +@smallexample if (int i = 7) @dots{} -@end example +@end smallexample where there is a new local variable (or variables) declared within the condition. @@ -1585,9 +1584,9 @@ the @code{LABEL_DECL} with @code{DECL_NAME}. If the function uses the G++ ``named return value'' extension, meaning that the function has been defined like: -@example +@smallexample S f(int) return s @{@dots{}@} -@end example +@end smallexample then there will be a @code{RETURN_INIT}. There is never a named returned value for a constructor. The first argument to the @code{RETURN_INIT} is the name of the object returned; the second @@ -1602,9 +1601,9 @@ constructed in the place where the object will be returned. Used to represent a @code{return} statement. The @code{RETURN_EXPR} is the expression returned; it will be @code{NULL_TREE} if the statement was just -@example +@smallexample return; -@end example +@end smallexample @item SCOPE_STMT @@ -1721,6 +1720,7 @@ This macro returns the attributes on the type @var{type}. @findex PTRMEM_CST_MEMBER @tindex VAR_DECL @tindex NEGATE_EXPR +@tindex ABS_EXPR @tindex BIT_NOT_EXPR @tindex TRUTH_NOT_EXPR @tindex ADDR_EXPR @@ -1803,9 +1803,9 @@ noted otherwise, the operands to an expression are accessed using the @code{TREE_OPERAND} macro. For example, to access the first operand to a binary plus expression @code{expr}, use: -@example +@smallexample TREE_OPERAND (expr, 0) -@end example +@end smallexample @noindent As this example indicates, the operands are zero-indexed. @@ -1819,10 +1819,11 @@ These nodes represent integer constants. Note that the type of these constants is obtained with @code{TREE_TYPE}; they are not always of type @code{int}. In particular, @code{char} constants are represented with @code{INTEGER_CST} nodes. The value of the integer constant @code{e} is -given by @example +given by +@smallexample ((TREE_INT_CST_HIGH (e) << HOST_BITS_PER_WIDE_INT) + TREE_INST_CST_LOW (e)) -@end example +@end smallexample @noindent HOST_BITS_PER_WIDE_INT is at least thirty-two on all platforms. Both @code{TREE_INT_CST_HIGH} and @code{TREE_INT_CST_LOW} return a @@ -1893,11 +1894,11 @@ or @code{UNION_TYPE} within which the pointer points), and the Note that the @code{DECL_CONTEXT} for the @code{PTRMEM_CST_MEMBER} is in general different from the @code{PTRMEM_CST_CLASS}. For example, given: -@example +@smallexample struct B @{ int i; @}; struct D : public B @{@}; int D::*dp = &D::i; -@end example +@end smallexample @noindent The @code{PTRMEM_CST_CLASS} for @code{&D::i} is @code{D}, even though the @code{DECL_CONTEXT} for the @code{PTRMEM_CST_MEMBER} is @code{B}, @@ -1913,6 +1914,23 @@ These nodes represent unary negation of the single operand, for both integer and floating-point types. The type of negation can be determined by looking at the type of the expression. +The behavior of this operation on signed arithmetic overflow is +controlled by the @code{flag_wrapv} and @code{flag_trapv} variables. + +@item ABS_EXPR +These nodes represent the absolute value of the single operand, for +both integer and floating-point types. This is typically used to +implement the @code{abs}, @code{labs} and @code{llabs} builtins for +integer types, and the @code{fabs}, @code{fabsf} and @code{fabsl} +builtins for floating point types. The type of abs operation can +be determined by looking at the type of the expression. + +This node is not used for complex types. To represent the modulus +or complex abs of a complex value, use the @code{BUILT_IN_CABS}, +@code{BUILT_IN_CABSF} or @code{BUILT_IN_CABSL} builtins, as used +to implement the C99 @code{cabs}, @code{cabsf} and @code{cabsl} +built-in functions. + @item BIT_NOT_EXPR These nodes represent bitwise complement, and will always have integral type. The only operand is the value to be complemented. @@ -1974,7 +1992,7 @@ real part and the second operand is the imaginary part. These nodes represent the conjugate of their operand. @item REALPART_EXPR -@item IMAGPART_EXPR +@itemx IMAGPART_EXPR These nodes represent respectively the real and the imaginary parts of complex numbers (their sole argument). @@ -2066,6 +2084,9 @@ The @code{TRUNC_MOD_EXPR} of two operands @code{a} and @code{b} is always @code{a - (a/b)*b} where the division is as if computed by a @code{TRUNC_DIV_EXPR}. +The behavior of these operations on signed arithmetic overflow is +controlled by the @code{flag_wrapv} and @code{flag_trapv} variables. + @item ARRAY_REF These nodes represent array accesses. The first operand is the array; the second is the index. To calculate the address of the memory @@ -2161,9 +2182,9 @@ sites. @item STMT_EXPR These nodes are used to represent GCC's statement-expression extension. The statement-expression extension allows code like this: -@example +@smallexample int f() @{ return (@{ int j; j = 3; j + 7; @}); @} -@end example +@end smallexample In other words, an sequence of statements may occur where a single expression would normally appear. The @code{STMT_EXPR} node represents such an expression. The @code{STMT_EXPR_STMT} gives the statement @@ -2172,13 +2193,13 @@ value of the expression is the value of the last sub-statement in the @code{COMPOUND_STMT}. More precisely, the value is the value computed by the last @code{EXPR_STMT} in the outermost scope of the @code{COMPOUND_STMT}. For example, in: -@example +@smallexample (@{ 3; @}) -@end example +@end smallexample the value is @code{3} while in: -@example +@smallexample (@{ if (x) @{ 3; @} @}) -@end example +@end smallexample (represented by a nested @code{COMPOUND_STMT}), there is no value. If the @code{STMT_EXPR} does not yield a value, it's type will be @code{void}. @@ -2214,10 +2235,7 @@ second operand is a @code{TREE_LIST}. If the @code{TREE_TYPE} of the @code{CONSTRUCTOR} is a @code{RECORD_TYPE} or @code{UNION_TYPE}, then the @code{TREE_PURPOSE} of each node in the @code{TREE_LIST} will be a @code{FIELD_DECL} and the @code{TREE_VALUE} of each node will be the -expression used to initialize that field. You should not depend on the -fields appearing in any particular order, nor should you assume that all -fields will be represented. Unrepresented fields may be assigned any -value. +expression used to initialize that field. If the @code{TREE_TYPE} of the @code{CONSTRUCTOR} is an @code{ARRAY_TYPE}, then the @code{TREE_PURPOSE} of each element in the @@ -2227,8 +2245,10 @@ again, the @code{TREE_VALUE} is the corresponding initializer. If the @code{TREE_PURPOSE} is @code{NULL_TREE}, then the initializer is for the next available array element. -Conceptually, before any initialization is done, the entire area of -storage is initialized to zero. +In the front end, you should not depend on the fields appearing in any +particular order. However, in the middle end, fields must appear in +declaration order. You should not assume that all fields will be +represented. Unrepresented fields will be set to zero. @item COMPOUND_LITERAL_EXPR @findex COMPOUND_LITERAL_EXPR_DECL_STMT |
