The task of the parser is to read the token fed by the scanner, and make sure that the pascal syntax is respected. It also populates the symbol table, and creates the intermediate nodes (the tree) which will be used by the code generator.
An overview of the parsing process, as well as its relationship with the tree the type checker and the code generator is shown in the following diagram:
Each module being compiled, be it a library , unit or main program has some information which is required. This is stored in the tmodule object in memory. To avoid recompilation of already compiled module, the dependencies of the modules is stored in a PPU file, which makes it easier to determine which modules to recompile.
pascal
type
PModule =^TModule;
TModule =object(TLinkedList_Item)
PPUFile: PPPUFile;// Pointer to PPU file object (unit file)
Crc: Longint;// CRC-32 bit of the whole PPU file
Interface_CRC: Longint;// CRC-32 bit of the interface part of// the PPU file
Flags: Longint;// Unit file flags
Compiled: Boolean;// TRUE if module is already compiled
Do_Reload: Boolean;// TRUE if the PPU file must be reloaded
Do_Assemble: Boolean;// Only assemble, don’t recompile unit
Sources_Avail: Boolean;// TRUE if all sources of module are available
Sources_Checked: Boolean;// TRUE if the sources has already been checked
Is_Unit: Boolean;// TRUE if this is a unit (otherwise a library // or a main program)
In_Compile: Boolean;// module is currently being recompiled
In_Second_Compile: Boolean;// module is being compiled for second time
In_Second_Load: Boolean;// module is being reloaded a second time
In_Implementation: Boolean;// currently compiling implementation part // (units only)
In_Global: Boolean;// currently compiling implementation part// (units only)
Recompile_Reason: TRecompile_Reason;// Reason why module should be recompiled
Islibrary: Boolean;// TRUE if this module is a shared library
Map: PUnitMap;// Map of all used units for this unit
Unitcount: Word;// Internal identifier of unit (for GDB support)
Unit_index: Word;
Globalsymtable: Pointer;// Symbol table for this module of externally// visible symbols
Localsymtable: Pointer;// Symbol table for this module of locally// visible symbols
Scanner: Pointer;// Scanner object pointer
Loaded_From: PModule;// Module which referred to this module
Uses_Imports: Boolean;// TRUE if this module imports symbols// from a shared library
Imports: PLinkedList;// Linked list of imported symbols
_Exports: PLinkedList;// Linked list of exported symbols (libraries only)
SourceFiles: PFileManager;// List of all source files for this module
ResourceFiles: TStringContainer;// List of all resource files for this module
Used_Units: TLinkedList;// Information on units used by this module // (pused_unit)
Dependent_Units: TLinkedList;
LocalUnitSearchPath,// Search path for obtaining module source code
LocalObjectSearchPath,
LocalIncludeSearchPath,// Search path for includes for this module
LocalLibrarySearchPath: TSearchPathList;
Path: PString;// Path were module is located or created
OutputPath: PString;// Path where object files (unit), // executable (program) or // shared library (library) is created
ModuleName: PString;// Name of the module in uppercase
ObjFileName: PString;// Full name of object file or executable file
AsmFileName: PString;// Full name of the assembler file
PPUFileName: PString;// Full name of the PPU file
StaticLibFilename: PString;// Full name of the static library name// (used when smart linking is used)
SharedLibFilename: PString;// Filename of the output shared library// (in the case of a library)
ExeFileName: PString;// Filename of the output executable// (in the case of a program)
AsmPrefix: PString;// Filename prefix of output assembler// files when using smartlinking
MainSource: PString;// Name of the main source fileend;
Parse types
(last updated for fpc version 1.0.x)
Entry
program or library parsing
unit parsing
routine parsing
label declarations
constant declarations
type declarations
variable declarations
thread variable declarations
resource string declarations
exports declaration
expression parsing
typed constant declarations
Parser interface
(last updated for fpc version 1.0.x)
variables
AktProcSym
Declaration:
var`` AktProcSym: PProcSym;
Description:
Pointer to the symbol information for the routine currently being parsed.
LexLevel
<tbody>
0 = for main program<br />
1 = for subroutine<br />
2 = for local / nested subroutines.</td>
</tbody>
Current_Module
Declaration:
var`` Current_Module: PModule;
Description:
Information on the current module (program, library or unit) being compiled.
The following variables are default type definitions which are created each time compilation begins (default system-unit definitions), these definitions should always be valid:
VoidDef
Declaration:
var`` VoidDef: POrdDef;
Description:
Pointer to nothing type
Notes:
This is loaded as a default supported type for the compiler
cCharDef
Declaration:
var`` cCharDef: POrdDef;
Description:
Type definition for a character (char)
Notes:
This is loaded as a default supported type for the compiler
cWideCharDef
Declaration:
var`` cWideCharDef: POrdDef;
Description:
Type definition for a unicode character (WideChar)
Notes:
This is loaded as a default supported type for the compiler
BoolDef
Declaration:
var`` BoolDef: POrdDef;
Description:
Type definition for a boolean value (boolean)
Notes:
This is loaded as a default supported type for the compiler
u8BitDef
Declaration:
var`` u8BitDef: POrdDef;
Description:
Type definition for an 8-nit unsigned value (byte)
Notes:
This is loaded as a default supported type for the compiler
u16BitDef
Declaration:
var`` u16BitDef: POrdDef;
Description:
Type definition for an unsigned 16-bit value (word)
Notes:
This is loaded as a default supported type for the compiler
u32BitDef
Declaration:
var`` u32BitDef: POrdDef;
Description:
Type definition for an unsigned 32-bit value (cardinal)
Notes:
This is loaded as a default supported type for the compiler
s32BitDef
Declaration:
var`` s32BitDef: POrdDef;
Description:
Type definition for a signed 32-bit value (Longint)
Notes:
This is loaded as a default supported type for the compiler
cu64BitDef
Declaration:
var`` cu64BitDef: POrdDef;
Description:
Type definition for an unsigned 64-bit value (QWord)
Notes:
This is loaded as a default supported type for the compiler
cs64BitDef
Declaration:
var`` cs64BitDef: POrdDef;
Description:
Type definition for a signed 64-bit value (Int64)
Notes:
This is loaded as a default supported type for the compiler
The following variables are default type definitions which are created each time compilation begins (default system-unit definitions), these definitions should always be valid:
s64FloatDef
Declaration:
var`` s64FloatDef: PFloatDef;
Description:
Type definition for a 64-bit IEEE floating point type (double)
Notes:
This is loaded as a default supported type for the compiler. This might not actually really point to the double type if the cpu does not support it.
s32FloatDef
Declaration:
var`` s32FloatDef: PFloatDef;
Description:
Type definition for a 32-bit IEEE floating point type (single)
Notes:
This is loaded as a default supported type for the compiler. This might not actually really point to the single type if the cpu does not support it.
s80FloatDef
Declaration:
var`` s80FloatDef : PFloatDef;
Description:
Type definition for an extended floating point type (extended)
Notes:
This is loaded as a default supported type for the compiler. This might not actually really point to the extended type if the cpu does not support it.
s32FixedDef
Declaration:
var`` s32FixedDef: PFloatDef;
Description:
Type definition for a fixed point 32-bit value (fixed)
Notes:
This is loaded as a default supported type for the compiler. This is not supported officially in FPC 1.0
The following variables are default type definitions which are created each time compilation begins (default system-unit definitions), these definitions should always be valid:
cShortStringDef
Declaration:
var`` cShortStringDef: PStringDef;
Description:
Type definition for a short string type (ShortString)
Notes:
This is loaded as a default supported type for the compiler.
cLongStringDef
Declaration:
var`` cLongStringDef: PStringDef;
Description:
Type definition for a long string type (LongString)
Notes:
This is loaded as a default supported type for the compiler.
cAnsiStringDef
Declaration:
var`` cAnsiStringDef: PStringDef;
Description:
Type definition for an ansistring type (AnsiString)
Notes:
This is loaded as a default supported type for the compiler.
cWideStringDef
Declaration:
var`` cWideStringDef: PStringDef;
Description:
Type definition for an wide string type (WideString)
Notes:
This is loaded as a default supported type for the compiler.
OpenShortStringDef
Declaration:
var`` OpenShortStringDef: PStringDef;
Description:
Type definition for an open string type (OpenString)
Notes:
This is loaded as a default supported type for the compiler.
OpenCharArrayDef
Declaration:
var`` OpenCharArrayDef: PArrayDef;
Description:
Type definition for an open char array type(OpenCharArray)
Notes:
This is loaded as a default supported type for the compiler.
The following variables are default type definitions which are created each time compilation begins (default system-unit definitions), these definitions should always be valid:
VoidPointerDef
Declaration:
var`` VoidPointerDef: PPointerDef;
Description:
Type definition for a pointer which can point to anything (Pointer)
Notes:
This is loaded as a default supported type for the compiler
CharPointerDef
Declaration:
var`` CharPointerDef: PPointerDef;
Description:
Type definition for a pointer which can point to characters (PChar)
Notes:
This is loaded as a default supported type for the compiler
VoidFarPointerDef
Declaration:
var`` VoidFarPointerDef: PPointerDef;
Description:
Type definition for a pointer which can point to anything (intra-segment) (far Pointer)
Notes:
This is loaded as a default supported type for the compiler
cFormalDef
Declaration:
var`` cFormalDef: PFormalDef;
Description:
Notes:
This is loaded as a default supported type for the compiler
cfFileDef
Declaration:
var`` cfFileDef: PFileDef;
Description:
This is the default file type (file)
Notes:
This is loaded as a default supported type for the compiler
From the Free Pascal wiki, page "The parser", as it stood on 2020-12-31 after a change by E-ric, out of the wiki's dump of 2024-05-26. Copyright stays with the author who wrote it, according to the old wiki's Licensing page. If you have concerns about this material, message the admin.