Symbol entries/fr

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Entrées de symbole



Avertissement: Dernière mise à jour pour FPC version 1.0.x

Il y a différents types de symbole possibles, chacun ayant différents champs des autres. Chaque symbole a une signature spécifique pour indiquer quel type d'entrée il s'agit. Chaque entrée dans la table de symboles est effectivement une des entrées de symbole décrite dans les sections suivantes. La relation entre une entrée de symbole, une définition de type, et l'entrée de symbole du nom de type est montrée dans la figure suivante:

Types d'entrée de symbole


Avertissement: Dernière mise à jour pour FPC version 1.0.x

Type de base de symbole (TSym)

All entries in the symbol table are derived from this base object which contains information on the symbol type as well as information on the owner of this symbol entry.

  PSym = ^TSym;
  TSym = object(TSymTableEntry)
    SymOptions: TSymOptions;  // Indicate the access scope of the symbol
    FileInfo: TFilePosInfo;
    Refs: Longint;            // Indicates how many times this label is refered in the
                              // parsed code (is only used with variable and assembler
                              // label symbols).
    LastRef: PRef;
    DefRef: PRef;
    LastWritten: PRef;
    RefCount: Longint;        // Browser information indicating the reference count
    Typ: TSymTyp;             // Indicates the symbol type
    IsStabWritten: Boolean;   // Set to TRUE if the stabs debugging information has
                              // been written for this symbol.
TSymTyp Description
AbstractSym This is a special abstract symbol (this should never occur)
VarSym This symbol is a variable declaration in the var section, or a var parameter.
TypeSym This symbol is a type name
ProcSym This symbol is a routine or method name
UnitSym This symbol is a unit name
ProgramSym This symbol is the main program name
ConstSym This symbol is a constant
EnumSym This symbol is an enumeration symbol (an element in an enumeration)
TypedConstSym This symbol is pre-initialized variable (pascal typed constant)
ErrorSym This symbol is created for error generation
SysSym This symbol represents an inlined system unit routine
LabelSym This symbol represents a label in a label pascal declaration
AbsoluteSym This symbol represents an the symbol following an absolute variable declaration
PropertySym This symbol is a property name
FuncRetSym This symbol is the name of the return value for functions
MacroSym This symbol is a macro symbol (just like #define in C)

Symbole Etiquette (TLabelSym)

The label symbol table entry is only created when a pascal label is declared via the label keyword. The object has the following fields which are available for use publicly:

  PLabelSym = ^TLabelSym;
  TLabelSym = object(TSym)
    Used: Boolean;                 // Set to TRUE if this pascal label is used using a goto
                                   // or in an assembler statement
    Defined: Boolean;              // Set to TRUE if this label has been declared
    Lab: PAsmLabel;                // Points to the actual assembler label structure which
                                   // will be emitted by the code generator
    Code: Pointer;

Symbole Unité (TUnitSym)

The unit symbol is created and added to the symbol table each time that the uses clause is parsed and a unit name is found, it is also used when compiling a unit, with the first entry in that symbol table being the unit name being compiled. The unit symbol entry is actual part of a linked list which is used in the unit symbol table.

  PUnitSym = ^TUnitSym;
  TUnitSym = object(TSym)
    UnitSymTable: PUnitSymTable;  // Pointer to the global symbol table for that
                                  // unit, containing entries for each public?
                                  // symbol in that unit
    PrevSym: PUnitSym;            // Pointer to previous entry in the linked list

Symbole Macro (TMacroSym)

The macro synbols are used in the preprocessor for conditional compilation statements. There is one such entry created for each $define directive, it contains the value of the define (stored as a string).

  PMacroSym = ^TMacroSym;
  TMacroSym = object(TSym)
    Defined: Boolean;              // TRUE if the symbol has been defined with a 
                                   // $define directive, or false if it has been 
                                   // undefined with a $undef directive
    Defined_At_Startup: Boolean;   // TRUE if the symbol is a system wide define
    Is_Used: Boolean;              // TRUE if the define has been used such as in 
                                   // a $ifdef directive.
    BufText: PChar;                // The actual string text of the define
    BufLength: Longint;            // The actual string length of the define

Symbole Erreur (TErrorSym)

This symbol is actually an empty symbol table entry. When the parser encounters an error when parsing a symbol, instead of putting nothing in the symbol table, it puts this symbol entry. This avoids illegal memory accesses later in parsing.

Symbole Procédure (TProcSym)

The procedure symbol is created each time a routine is defined in the code. This can be either a forward definition or the actual implementation of the routine. After creation, the symbol is added into the appropriate symbol table stack.

  PProcSym = ^TProcSym;
  TProcSym = object(TSym)
    Is_Global: Boolean;           // Set if the routine is exported by the unit
    Definition: PProcDef;         // Procedure definition, including parameter 
                                  // information and return values

Symbole Type (TTypeSym)

The type symbol is created each time a new type declaration is done, the current symbol table stack is then inserted with this symbol. Furthermore, each time the compiler compiles a module, the default base types are initialized and added into the symbol table (psystem.pas) The type symbol contains the name of a type, as well as a pointer to its type definition.

  PTypeSym = ^TTypeSym;
  TTypeSym = object(TSym)
    ResType: TType;               // Contains base type information as well as the type
                                  // definition

Symbole Variable (TVarSym)

Variable declarations, as well as parameters which are passed onto routines are declared as variable symbol types. Access information, as well as type information and optimization information are stored in this symbol type.

  PVarSym = ^TVarSym;
  TVarSym = object(TSym)
    Reg: TRegister;              // If the value is a register variable, the reg field will
                                 // be different then R_NO
    VarSpez: TVarSpez;           // Indicates the variable type (parameters only) (Cf. 32).
    Address: Longint;            // In the case where the variable is a routine parameter,
                                 // this indicates the positive offset from theframe_pointer 
                                 // to access this variable. In the caseof a local variable,
                                 // this field indicates the negative offset from the 
                                 // frame_pointer. to access this variable.
    LocalVarSym: PVarSym;
    VarType: TType;              // Contains base type information as well as the type
                                 // definition
    VarOptions: TVarOptions;     // Flags for this variable (Cf. 31)
    VarState: TVarState;         // Indicates the state of the variable, if it’s used or
                                 // declared

TVarOptions Description
vo_regable The variable can be put into a hardware general purpose register
vo_is_c_var The variable is imported from a C module
vo_is_external The variable is declared external
vo_is_Dll_var The variable is a shared library variable
vo_is_thread_var The variable is declared as being thread safe
vo_fpuregable The variable can be put into a hardware floating point register
vo_is_const unused and useless
vo_is_exported The variable is declared as exported in a dynamic link library

TVarSpez Description
vs_value This is a value parameter
vs_const This is a constant parameter, property or array
vs_var This is a variable parameter

Symbole Propriétét (TPropertySym)

  PPropertySym = ^TPropertySym;
  TPropertySym = object(TSym)
    PropOptions: TPropertyOptions;    // ???
    PropType: TType;                  // Indicates the type of the property
    PropOverriden: PPropertySym;      // ???
    IndexType: TType;
    Index: Longint;                   // ????
    Default: Longint;                 // ???
    ReadAccess: PSymList;             // ???
    WriteAccess: PSymList;            // ???
    StoredAccess: PSymList;           // ???

Symbole Valeur de retour de fonction


Symbole déclaré Absolute (TAbsoluteSym)

This symbol represents a variable declared with the absolute keyword. The address of the TVarSym object holds the address of the variable in the case of an absolute address variable.

The possible types of absolute symbols, are from an external object reference, an absolute address (for certain targets only), or on top of another declared variable.

  PAbsoluteSym = ^TAbsoluteSym;
  TAbsoluteSym = object(TVarSym)
    AbsTyp: TAbsoluteTyp;         // Indicates the type of absolute symbol it is 
    AbsSeg: Boolean;              // ???
    Ref: PSym;                    // In case abstyp is tovar, this field indicates the
                                  // symbol which is overlaid with this symbol. Otherwise
                                  // this field is unused.
    AsmName: PString;             // In case abstyp is toasm, this field indicates label
                                  // name for the variable.
TAbsoluteTyp Description
toVar The symbol will be declared on top of another symbol (variable or typed constant)
toAsm The variable is imported from an external module
toAddr The variable is declared as being at an absolute address

Symbole constante typée


Symbole Constante (TConstSym)

This symbol type will contain all constants defined and encountered during the parsing. The values of the constants are also set in this symbol type entry.

  PConstSym = ^TConstSym;
  TConstSym = object(TSym)
    ConstType: TType;       // Type information for this constant (?).
    ConstTyp: TConstTyp;    // Indicates the type of the constant
    ResStrIndex: Longint;   // If this is a resource string constant, it indicates the
                            // index in the resource table
    Value: Longint;         // In certain cases, contains the value of the constant
    Len: Longint;

Symbole Enumération


Symbole Programme

The program symbol type (TProgramSym) is used to store the name of the program, which is declared using program in the pascal source. This symbol type is currently unused in FreePascal.

Symbole Sys

The TSysSym symbol type is used to load indexes into the symbol table of the internal routines which are inlined directly by the compiler. It has a single field, which is the index of the inline routine.

Symbole Interface

Prochain chapitre: Information de type