Numerous data structures are available for implementing tables. Trees, linear lists and self-organizing lists can all be used to implement a symbol table. The symbol table is accessed by most phases of a compiler, beginning with lexical analysis, and continuing through optimization. A compiler may use one large symbol table for all symbols or use separated, hierarchical symbol tables for different scopes.
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In Linux, the `System.map` file is a symbol table used by the kernel. A symbol table is a look-up between symbol names and their addresses in memory. A symbol name may be the name of a variable or the name of a function.
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Similarly, OpenCog provides a dynamic symbol table, called the atomspace, which is used for knowledge representation.
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The COFF symbolic debugging information consists of symbolic (string) names for program functions and variables, and line number information, used for setting breakpoints and tracing execution. Symbolic names are stored in the COFF symbol table. Each symbol table entry includes a name, storage class, type, value and section number. Short names (8 characters or fewer) are stored directly in the symbol table; longer names are stored as an offset into the string table at the end of the COFF object.
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SAP is a two-pass assembler. It is capable of running on a 704 with a minimum of 4 K 36-bit words of core storage. This configuration allows up to 1097 entries in the symbol table. Additional core memory beyond 4 KW can be used to allow for additional symbol table entries.
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DynamoRIO contains libraries that extend its API to provide symbol table access, function wrapping and replacing, and memory address tracing utilities.
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Not all of this information is included in the output file, but may be provided for use in debugging. In many cases, the symbol's cross-reference information is stored with or linked to the symbol table. Most compilers print some or all of this information in symbol table and cross-reference listings at the end of translation.
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Intel HEX format was often used with Intel processors. TekHex is another hex format that can include a symbol table for debugging.
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In computer science, a symbol table is a data structure used by a language translator such as a compiler or interpreter, where each identifier (or symbol) in a program's source code is associated with information relating to its declaration or appearance in the source. In other words, the entries of a symbol table store the information related to the entry's corresponding symbol.
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A symbol table must be organised in such a way that entries can be found as quickly as possible. Hash tables are usually used to organise a symbol table, where the keyword or identifier is 'hashed' to produce an array subscript. Collisions are inevitable in a hash table, and a common way of handling them is to store the synonym in the next available free space in the table.
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The implementations of dynamic loading on UNIX-like operating systems and Windows allow programmers to extract symbols from the currently executing process. UNIX-like operating systems allow programmers to access the global symbol table, which includes both the main executable and subsequently loaded dynamic libraries. Windows allows programmers to access symbols exported by the main executable. Windows does not use a global symbol table, and has no API to search across multiple modules to find a symbol by name.
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Some programming languages allow the symbol table to be manipulated at run-time, so that symbols can be added at any time. Racket is an example of such a languageSymbols - Racket Documentation. Both the LISP and the Scheme programming languages allow arbitrary, generic properties to be associated with each symbol.Symbols - Guile Documentation The Prolog programming language is essentially a symbol-table manipulation language; symbols are called atoms, and the relationships between symbols can be reasoned over.
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Note that the decimal offsets are number of characters, not line or string number within the "//" file. This is usually the second entry of the file, after the symbol table which always is the first. System V ar uses the special filename "/" to denote that the following data entry contains a symbol lookup table, which is used in ar libraries to speed up access. This symbol table is built in three parts which are recorded together as contiguous data.
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The a.out support for debug information is done through the use of special entries in the symbol table called stabs. The stabs format has also been used in many COFF and ELF variations.
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This process continues until all external references have been resolved. It is an error if one or more remains unresolved at the end of the process. While reverse engineering an executable, many tools refer to the symbol table to check what addresses have been assigned to global variables and known functions. If the symbol table has been stripped or cleaned out before being converted into an executable, tools will find it harder to determine addresses or understand anything about the program.
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A symbol in computer programming is a primitive data type whose instances have a unique human-readable form. Symbols can be used as identifiers. In some programming languages, they are called atoms. Uniqueness is enforced by holding them in a symbol table.
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A core dump represents the complete contents of the dumped regions of the address space of the dumped process. Depending on the operating system, the dump may contain few or no data structures to aid interpretation of the memory regions. In these systems, successful interpretation requires that the program or user trying to interpret the dump understands the structure of the program's memory use. A debugger can use a symbol table, if one exists, to help the programmer interpret dumps, identifying variables symbolically and displaying source code; if the symbol table is not available, less interpretation of the dump is possible, but there might still be enough possible to determine the cause of the problem.
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The Windows (PE/COFF) variant is based on the SysV/GNU variant. The first entry "/" has the same layout as the SysV/GNU symbol table. The second entry is another "/", a Microsoft ECOFF extension that stores an extended symbol cross-reference table. This one is sorted and uses little-endian integers.
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In an elementary form, the dictionary entries represent nodes in a directed acyclic graph (DAG), that describes the actions of the program, as an abstract syntax tree (AST) in tabular form. It uses an intermediate representation (IR), that is based on the encoded abstract syntax tree and symbol table of a program.
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Each pointer corresponds to a symbol in the object; thus, these pointers create a relation between a symbol and a DT_NEEDED entry. This allows the linker to locate the library specified by a particular DT_NEEDED entry and check only its symbol table for each symbol, rather than iterate through potentially every library for every symbol.
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The code comments and symbol table information are processed by Ddoc into an internal structured format. Each of these structures corresponds to a template expressed as a macro. The template macros convert the structured format into another set of macros that express the markup. The latter set of markup macros are expanded to produce, by default, HTML.
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Mach-O, short for Mach object file format, is a file format for executables, object code, shared libraries, dynamically-loaded code, and core dumps. A replacement for the a.out format, Mach-O offers more extensibility and faster access to information in the symbol table. Mach-O is used by most systems based on the Mach kernel.
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Processor code looks like and executes similar to JCL. Processors can use both Endevor symbols and Endevor variables. Endevor systems are defined by a specific symbol table which is essentially a list of name pair values. Where a processor is not defined to a type / processor group / function, being generate delete or move, the default processor is invoked.
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In the second form, the entry identifies a symbol table entry representing the start of a function, enabling a breakpoint to be set using the function's name. Note that COFF was not capable of representing line numbers or debugging symbols for included source as with header files rendering the COFF debugging information virtually useless without incompatible extensions.
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A symbol table may only exist in memory during the translation process, or it may be embedded in the output of the translation, such as in an ABI object file for later use. For example, it might be used during an interactive debugging session, or as a resource for formatting a diagnostic report during or after execution of a program.
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The minimum information contained in a symbol table used by a translator includes the symbol's name, its relocatability attributes (absolute, relocatable, etc.), and its location or address. For relocatable symbols, some relocation information must be stored. Symbol tables for high-level programming languages store the symbol's type: string, integer, floating-point, etc., its size, and its dimensions and its bounds.
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SQUOZE (abbreviated as SQZ) is a memory-efficient representation of a combined source and relocatable object program file with a symbol table on punched cards which was introduced in 1958 with the SCAT assembler on the SHARE Operating System (SOS) for the IBM 709. A program in this format was called a SQUOZE deck. It was also used on later machines including the IBM 7090 and 7094.
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Various Unix-like operating systems provide the loop device functionality using different names. In Linux, device names are encoded in the symbol table entries of their corresponding device drivers. The device is called a "loop" device and device nodes are usually named /dev/loop0, /dev/loop1, etc. They can be created with makedev for the static device directory, dynamically by the facilities of the device filesystem (udev), or directly with mknod.
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Symbol table for non-verbal communication with patients According to some authors, nonverbal communication represents two- thirds of all communications. Nonverbal communication can portray a message both vocally and with the correct body signals or gestures. Body signals comprise physical features, conscious and unconscious gestures and signals, and the mediation of personal space. The wrong message can also be established if the body language conveyed does not match a verbal message.
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For example, in a scoped language such as Algol or PL/I a symbol "p" can be declared separately in several procedures, perhaps with different attributes. The scope of each declaration is the section of the program in which references to "p" resolve to that declaration. Each declaration represents a unique identifier "p". The symbol table must have some means of differentiating references to the different "p"s.
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The version of in GNU binutils and elfutils have an additional "thin archive" format with the magic number . A thin archive only contains a symbol table and references to the file. The file format is essentially a System V format archive where every file is stored without the data sections. Every filename is stored as a "long" filename and they are to be resolved as if they were symbolic links.
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Secondly, it allows the executables also to be used as shared libraries, if they have a symbol table. Typical combined executable and shared library formats are ELF and Mach-O (both in Unix) and PE (Windows). In some older environments such as 16-bit Windows or MPE for the HP 3000 only stack-based data (local) was allowed in shared-library code, or other significant restrictions were placed on shared- library code.
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Linux kernel boot and decompression process On Linux systems, `vmlinux` is a statically linked executable file that contains the Linux kernel in one of the object file formats supported by Linux, which includes ELF, COFF and a.out. The `vmlinux` file might be required for kernel debugging, symbol table generation or other operations, but must be made bootable before being used as an operating system kernel by adding a multiboot header, bootsector and setup routines.
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There is a large library of utility objects, and the language provides basic support for object-oriented programming. Unlike many other programming languages, Visual Basic is generally not case-sensitive—though it transforms keywords into a standard case configuration and forces the case of variable names to conform to the case of the entry in the symbol table. String comparisons are case sensitive by default. The Visual Basic compiler is shared with other Visual Studio languages (C, C++).
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A common data structure used to implement symbol tables is the hash table. The time for searching in hash tables is independent of the number of elements stored in the table, so it is efficient for a large number of elements. It also simplifies the classification of literals in tabular format. As the lexical analyser spends a great proportion of its time looking up the symbol table, this activity has a crucial effect on the overall speed of the compiler.
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An object file will contain a symbol table of the identifiers it contains that are externally visible. During the linking of different object files, a linker will identify and resolve these symbol references. Usually all undefined external symbols will be searched for in one or more object libraries. If a module is found that defines that symbol it is linked with together with the first object file, and any undefined external identifiers are added to the list of identifiers to be looked up.
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The solution generally consists of feeding information from the semantic symbol table back into the lexer. That is, rather than functioning as a pure one-way pipeline from the lexer to the parser, there is a backchannel from semantic analysis back to the lexer. This mixing of parsing and semantic analysis is generally regarded as inelegant, which is why it is called a "hack". Without added context, the lexer cannot distinguish type identifiers from other identifiers because all identifiers have the same format.
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A JVM language is any language with functionality that can be expressed in terms of a valid class file which can be hosted by the Java Virtual Machine. A class file contains Java Virtual Machine instructions (Java byte code) and a symbol table, as well as other ancillary information. The class file format is the hardware- and operating system-independent binary format used to represent compiled classes and interfaces. There are several JVM languages, both old languages ported to JVM and completely new languages.
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Assembly directives, also called pseudo-opcodes, pseudo-operations or pseudo-ops, are commands given to an assembler "directing it to perform operations other than assembling instructions". Directives affect how the assembler operates and "may affect the object code, the symbol table, the listing file, and the values of internal assembler parameters". Sometimes the term pseudo-opcode is reserved for directives that generate object code, such as those that generate data. The names of pseudo-ops often start with a dot to distinguish them from machine instructions.
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The `nm` command ships with a number of later versions of Unix and similar operating systems including Plan 9. `nm` is used to examine binary files (including libraries, compiled object modules, shared-object files, and standalone executables) and to display the contents of those files, or meta information stored in them, specifically the symbol table. The output from `nm` distinguishes between various symbol types. For example, it differentiates between a function that is supplied by an object module and a function that is required by it.
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An illustration of the linking process. Object files and static libraries are assembled into a new library or executable Programs written in a high level language are either directly executed by some kind of interpreter or converted into machine code by a compiler (and assembler and linker) for the CPU to execute. While compilers (and assemblers) generally produce machine code directly executable by computer hardware, they can often (optionally) produce an intermediate form called object code. This is basically the same machine specific code but augmented with a symbol table with names and tags to make executable blocks (or modules) identifiable and relocatable.
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DMS provides attribute grammar evaluators for computing custom analyses over ASTs, such as metrics, and including special support for symbol table construction. Other program facts can be extracted by built-in control- and data- flow analysis engines, local and global pointer analysis, whole-program call graph extraction, and symbolic range analysis by abstract interpretation. Changes to ASTs can be accomplished by both procedural methods coded in PARLANSE and source-to-source tree transformations coded as rewrite rules using surface-syntax conditioned by any extracted program facts, using DMS's Rule Specification Language (RSL). The rewrite rule engine supporting RSL handles associative and commutative rules.
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A debug symbol is a special kind of symbol that attaches additional information to the symbol table of an object file, such as a shared library or an executable. This information allows a symbolic debugger to gain access to information from the source code of the binary, such as the names of identifiers, including variables and routines. The symbolic information may be compiled together with the module's binary file, or distributed in a separate file, or simply discarded during the compilation and/or linking. This information can be helpful while trying to investigate and fix a crashing application or any other fault.
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These examples all only require lexical context, and while they complicate a lexer somewhat, they are invisible to the parser and later phases. A more complex example is the lexer hack in C, where the token class of a sequence of characters cannot be determined until the semantic analysis phase, since typedef names and variable names are lexically identical but constitute different token classes. Thus in the hack, the lexer calls the semantic analyzer (say, symbol table) and checks if the sequence requires a typedef name. In this case, information must flow back not from the parser only, but from the semantic analyzer back to the lexer, which complicates design.
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BFD works by presenting a common abstract view of object files. An object file has a "header" with descriptive info; a variable number of "sections" that each has a name, some attributes, and a block of data; a symbol table; relocation entries; and so forth. Internally, BFD translates the data from the abstract view into the details of the bit/byte layout required by the target processor and file format. Its key services include handling byte order differences, such as between a little- endian host and big-endian target, correct conversion between 32-bit and 64-bit data, and details of address arithmetic specified by relocation entries.
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When linking a shared library or dynamic linked executable, the linker normally populates the symbol table for that library with all required symbols. It adds symbols in the current object with their offset, and leaves undefined symbols in the object unresolved. Unresolved symbols must still be known at link time, but the linker is passed shared libraries to link with and, when it finds a symbol in another library, it places a note in the output library indicating that it depends on these other shared libraries. This kind of weak linking forces the dynamic linker to resolve which library contains which symbol when the executable is run.
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It supports a long term compiling listener session which gives the compiler knowledge about the state of the compiled and thus running program, including the symbol table. This, in addition to dynamic linking, allows a function to be edited, recompiled, uploaded, and inserted into a running game without having to restart. The process is similar to the edit and continue feature offered by some C++ compilers, but allows programs to replace arbitrary amounts of code (even up to entire object files), and does not interrupt the running game with the debugger. This feature was used to implement code and to level streaming in the Jak and Daxter games.
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The pretokenization mechanism includes several minor mechanisms for assisting the pre-processor: caching of file existence and datestamp information, and recording inclusion guards so that guarded code can be quickly skipped over. Later clang development thus introduced a fully fledged precompiled header mechanism. This both tokenizes the input source code and performs syntactic and semantic analyses of it, writing out the compiler's internal generated abstract syntax tree (AST) and symbol table to a precompiled header file. Compared to the pretokenized header mechanism, this scales much better, as when reading the precompiled header file back in the compiler is not constrained by the fact that the input is a stream (of lexical tokens) to read the file linearly, using sequential I/O.
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There are also special-purpose tools called dump analyzers to analyze dumps. One popular tool, available on many operating systems, is the GNU binutils' objdump. On modern Unix-like operating systems, administrators and programmers can read core dump files using the GNU Binutils Binary File Descriptor library (BFD), and the GNU Debugger (gdb) and objdump that use this library. This library will supply the raw data for a given address in a memory region from a core dump; it does not know anything about variables or data structures in that memory region, so the application using the library to read the core dump will have to determine the addresses of variables and determine the layout of data structures itself, for example by using the symbol table for the program undergoing debugging.
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Elaine M. McGraw (née Boehme) was an American computer programmer who, together with Arthur Samuel and Gene Amdahl, invented open addressing based hash tables in 1954. After studying economics, McGraw began working as a computer programmer for The Prudential Life Insurance Company in the early 1950s, using a UNIVAC computer. Prudential sent her to IBM to learn how to program the IBM 701, but (believing that Prudential would not purchase this computer) she applied for a job at IBM, and was hired there in 1953 by Gene Amdahl. She continued to work at IBM until at least 1970.. In 1954, McGraw was working with Amdahl and Arthur Samuel on an assembler (a program for converting a textual description of a sequence of computer instructions into machine code) and she was tasked with implementing a symbol table for it.
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Microprocessor cards of Synte 2 speech synthesizer (1979) Synte 2 speech synthesizer for speech impaired people (1979) Synte 2 speech synthesizer on the table (1979) Synte 2 speech synthesizer and symbol table (1979) Speech Processing System SPS-01 (1979) Synte 2 speech synthesizer at the Invention Exhibition at the Museum Center Vapriikki in Tampere, Finland, picture 1 (June 20, 2012–) Synte 2 speech synthesizer at the Invention Exhibition at the Museum Center Vapriikki in Tampere, Finland, picture 2 (June 20, 2012–) Synte 2 speech synthesizer at the Invention Exhibition at the Museum Center Vapriikki in Tampere, Finland, picture 3 (June 20, 2012–) Matti Antero Karjalainen (April 2, 1946 – May 30, 2010) studied electronics at the Tampere University of Technology and received a doctoral degree on speech synthesis in 1978. He developed Synte 2 the first portable microprocessor-based text-to- speech synthesizer in the world. He was the head of Acoustics Laboratory at the Helsinki University of Technology from 1980 to 2006. He is speech synthesis, speech analysis, speech technology, audio signal processing and psychoacoustics pioneer in Finland.
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LOAD HELLO LINK: Loading EXIT .SAVE HELLO saved .RUN Hello, world! . The assembly listing file generated by the `/DLIST` (Disk LISTing) option to the `COMPILE` command: HELLO WORLD MACRO %53B(1247) 17:29 7-Apr-:9 Page 1 HELLO MAC 7-Apr-:9 17:29 TITLE HELLO WORLD ; 'Hello world' in MACRO-10 for TOPS-10 SEARCH UUOSYM ; Make UUO symbol names available 000000' 110 145 154 154 157 LAB: ASCIZ /Hello, world! 000001' 054 040 167 157 162 000002' 154 144 041 015 012 / ; NUL-terminated ASCII string with CRLF 000003' 000 000 000 000 000 000004' 047 00 0 00 000000 START: RESET ; Initialise job to clean runtime state 000005' 051 03 0 00 000000' OUTPUT: OUTSTR LAB ; Output string starting at LAB: 000006' 047 01 0 00 000012 MONRT. ; Return to monitor 000007' 254 00 0 00 000005' JRST OUTPUT ; Restart at OUTPUT: if user CONTINUEs job 000004' END START ; End assembly, set program start address NO ERRORS DETECTED PROGRAM BREAK IS 000010 CPU TIME USED 58:25.100 36P CORE USED HELLO WORLD MACRO %53B(1247) 17:29 7-Apr-:9 Page S-1 HELLO MAC 7-Apr-:9 17:29 SYMBOL TABLE LAB 000000' MONRT. 047040 000012 OUTPUT 000005' OUTSTR 051140 000000 RESET 047000 000000 START 000004' The date ":9" is a Year 2000 problem. A more complex MACRO-10 example program, which renders one version of the 99 Bottles of Beer song, may be examined at the "99 Bottles of Beer" web site.
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