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a.out(4) Kernel Interfaces Manual a.out(4) NAME a.out - Assembler and link editor output SYNOPSIS #include <a.out.h> DESCRIPTION a.out is the output file format of the assembler as(1) and the link ed- itor ld(1). Both programs make a.out executable if there were no er- rors and no unresolved external references. The debugger uses the a.out file to provide symbolic information to the user. The compilers and operating systems use a file format that is similar to standard System V COFF (common object file format). The File Header definition is based on the System V header file file- hdr.h, with the following changes (also see filehdr(4)): The symbol ta- ble file pointer, f_symptr, and the number of symbol table entries, f_nsyms, specify the file pointer and the size of the Symbolic Header, respectively. All tables that specify symbolic information have their file pointers and number of entries in the Symbolic Header. The Optional Header definition has the same format as the System V header file aouthdr.h (the ``standard'' (pre-COFF) UNIX system a.out header), except that the following fields have been added: bss_start, gprmask, cprmask, gp_value, and bldrev. (The bldrev field contains a number that reflects the release level of the compiler or assembler that created the executable.) The Section Header definition has the same format as the System V header file scnhdr.h. The relocation information definition is similar to that in Berkeley 4.3BSD UNIX, which has ``local'' relocation types (see reloc(4)). The a.out file is organized as follows: File Header Optional Header Section Headers Section Data -- includes text, read-only data, large data, 8- and 4-byte literal pools, small data, small bss (0 size), and large bss (0 size), as well as the shared library information. Section Relocation Information -- includes information for text, read-only data, large data, 8- and 4-byte literal pools, and small data. Sym- bolic Header -- missing if fully stripped. Line Numbers -- created only if debugging is on, and missing if stripped of nonglobals or fully stripped. Procedure Descriptor Table -- missing if fully stripped. Local Symbols -- missing if stripped of nonglobals or fully stripped. Optimization Symbols -- created only if debugging is on, and missing if stripped of nonglobals or fully stripped. Auxiliary Symbols -- created only if debugging is on, and missing if stripped of nonglobals or fully stripped. Local Strings -- missing if stripped of nonglobals or fully stripped. External Strings -- missing if fully stripped. Relative File Descriptors -- missing if stripped of nonglobals or fully stripped. File Descriptors -- missing if stripped of nonglobals or fully stripped. External Symbols -- missing if fully stripped. RELATED INFORMATION linenum(4), filehdr(4), reloc(4), scnhdr(4), syms(4). as(1), dbx(1), ld(1), nm(1), strip(1) delim off a.out(4)