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diff --git a/man-pages-posix-2017/man3p/dlopen.3p b/man-pages-posix-2017/man3p/dlopen.3p new file mode 100644 index 0000000..b456570 --- /dev/null +++ b/man-pages-posix-2017/man3p/dlopen.3p @@ -0,0 +1,270 @@ +'\" et +.TH DLOPEN "3P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual" +.\" +.SH PROLOG +This manual page is part of the POSIX Programmer's Manual. +The Linux implementation of this interface may differ (consult +the corresponding Linux manual page for details of Linux behavior), +or the interface may not be implemented on Linux. +.\" +.SH NAME +dlopen +\(em open a symbol table handle +.SH SYNOPSIS +.LP +.nf +#include <dlfcn.h> +.P +void *dlopen(const char *\fIfile\fP, int \fImode\fP); +.fi +.SH DESCRIPTION +The +\fIdlopen\fR() +function shall make the symbols (function identifiers and data object +identifiers) in the executable object file specified by +.IR file +available to the calling program. +.P +The class of executable object files eligible for this operation and +the manner of their construction are implementation-defined, though +typically such files are shared libraries or programs. +.P +Implementations may permit the construction of embedded dependencies in +executable object files. In such cases, a +\fIdlopen\fR() +operation shall load those dependencies in addition to the executable +object file specified by +.IR file . +Implementations may also impose specific constraints on the construction +of programs that can employ +\fIdlopen\fR() +and its related services. +.P +A successful +\fIdlopen\fR() +shall return a symbol table handle which the caller may use on subsequent +calls to +\fIdlsym\fR() +and +\fIdlclose\fR(). +.P +The value of this symbol table handle should not be interpreted in any +way by the caller. +.P +The +.IR file +argument is used to construct a pathname to the executable object file. If +.IR file +contains a +<slash> +character, the +.IR file +argument is used as the pathname for the file. Otherwise, +.IR file +is used in an implementation-defined manner to yield a pathname. +.P +If +.IR file +is a null pointer, +\fIdlopen\fR() +shall return a global symbol table handle for the currently running +process image. This symbol table handle shall provide access to the +symbols from an ordered set of executable object files consisting of +the original program image file, any executable object files loaded +at program start-up as specified by that process file (for example, +shared libraries), and the set of executable object files loaded using +\fIdlopen\fR() +operations with the RTLD_GLOBAL flag. As the latter set of executable +object files can change during execution, the set of symbols made +available by this symbol table handle can also change dynamically. +.P +Only a single copy of an executable object file shall be brought into +the address space, even if +\fIdlopen\fR() +is invoked multiple times in reference to the executable object file, +and even if different pathnames are used to reference the executable +object file. +.P +The +.IR mode +parameter describes how +\fIdlopen\fR() +shall operate upon +.IR file +with respect to the processing of relocations and the scope of visibility +of the symbols provided within +.IR file . +When an executable object file is brought into the address space of a +process, it may contain references to symbols whose addresses are not +known until the executable object file is loaded. +.P +These references shall be relocated before the symbols can be accessed. The +.IR mode +parameter governs when these relocations take place and may have the +following values: +.IP RTLD_LAZY 12 +Relocations shall be performed at an implementation-defined time, +ranging from the time of the +\fIdlopen\fR() +call until the first reference to a given symbol occurs. Specifying +RTLD_LAZY should improve performance on implementations supporting dynamic +symbol binding since a process might not reference all of the symbols +in an executable object file. And, for systems supporting dynamic symbol +resolution for normal process execution, this behavior mimics the normal +handling of process execution. +.IP RTLD_NOW 12 +All necessary relocations shall be performed when the executable object +file is first loaded. This may waste some processing if relocations are +performed for symbols that are never referenced. This behavior may be +useful for applications that need to know that all symbols referenced +during execution will be available before +\fIdlopen\fR() +returns. +.P +Any executable object file loaded by +\fIdlopen\fR() +that requires relocations against global symbols can reference the symbols +in the original process image file, any executable object files loaded +at program start-up, from the initial process image itself, from any +other executable object file included in the same +\fIdlopen\fR() +invocation, and any executable object files that were loaded in any +\fIdlopen\fR() +invocation and which specified the RTLD_GLOBAL flag. To determine the +scope of visibility for the symbols loaded with a +\fIdlopen\fR() +invocation, the +.IR mode +parameter should be a bitwise-inclusive OR with one of the following +values: +.IP RTLD_GLOBAL 12 +The executable object file's symbols shall be made available for +relocation processing of any other executable object file. In addition, +symbol lookup using +.IR dlopen (NULL, mode ) +and an associated +\fIdlsym\fR() +allows executable object files loaded with this mode to be searched. +.IP RTLD_LOCAL 12 +The executable object file's symbols shall not be made available for +relocation processing of any other executable object file. +.P +If neither RTLD_GLOBAL nor RTLD_LOCAL is specified, the default behavior +is unspecified. +.P +If an executable object file is specified in multiple +\fIdlopen\fR() +invocations, +.IR mode +is interpreted at each invocation. +.P +If RTLD_NOW has been specified, all relocations shall have been completed +rendering further RTLD_NOW operations redundant and any further RTLD_LAZY +operations irrelevant. +.P +If RTLD_GLOBAL has been specified, the executable object file shall +maintain the RTLD_GLOBAL status regardless of any previous or future +specification of RTLD_LOCAL, as long as the executable object file +remains in the address space (see +.IR "\fIdlclose\fR\^(\|)"). +.P +Symbols introduced into the process image through calls to +\fIdlopen\fR() +may be used in relocation activities. Symbols so introduced may duplicate +symbols already defined by the program or previous +\fIdlopen\fR() +operations. To resolve the ambiguities such a situation might present, +the resolution of a symbol reference to symbol definition is based on a +symbol resolution order. Two such resolution orders are defined: load +order and dependency order. Load order establishes an ordering among +symbol definitions, such that the first definition loaded (including +definitions from the process image file and any dependent executable +object files loaded with it) has priority over executable object files +added later (by +\fIdlopen\fR()). +Load ordering is used in relocation processing. Dependency ordering uses +a breadth-first order starting with a given executable object file, +then all of its dependencies, then any dependents of those, iterating +until all dependencies are satisfied. With the exception of the global +symbol table handle obtained via a +\fIdlopen\fR() +operation with a null pointer as the +.IR file +argument, dependency ordering is used by the +\fIdlsym\fR() +function. Load ordering is used in +\fIdlsym\fR() +operations upon the global symbol table handle. +.P +When an executable object file is first made accessible via +\fIdlopen\fR(), +it and its dependent executable object files are added in dependency +order. Once all the executable object files are added, relocations are +performed using load order. Note that if an executable object file or +its dependencies had been previously loaded, the load and dependency +orders may yield different resolutions. +.P +The symbols introduced by +\fIdlopen\fR() +operations and available through +\fIdlsym\fR() +are at a minimum those which are exported as identifiers of global +scope by the executable object file. Typically, such identifiers shall +be those that were specified in (for example) C source code as having +.BR extern +linkage. The precise manner in which an implementation constructs +the set of exported symbols for an executable object file is +implementation-defined. +.SH "RETURN VALUE" +Upon successful completion, +\fIdlopen\fR() +shall return a symbol table handle. If +.IR file +cannot be found, cannot be opened for reading, is not of an appropriate +executable object file format for processing by +\fIdlopen\fR(), +or if an error occurs during the process of loading +.IR file +or relocating its symbolic references, +\fIdlopen\fR() +shall return a null pointer. More detailed diagnostic information shall +be available through +\fIdlerror\fR(). +.SH ERRORS +No errors are defined. +.LP +.IR "The following sections are informative." +.SH EXAMPLES +Refer to +.IR "\fIdlsym\fR\^(\|)". +.SH "APPLICATION USAGE" +None. +.SH RATIONALE +None. +.SH "FUTURE DIRECTIONS" +None. +.SH "SEE ALSO" +.IR "\fIdlclose\fR\^(\|)", +.IR "\fIdlerror\fR\^(\|)", +.IR "\fIdlsym\fR\^(\|)" +.P +The Base Definitions volume of POSIX.1\(hy2017, +.IR "\fB<dlfcn.h>\fP" +.\" +.SH COPYRIGHT +Portions of this text are reprinted and reproduced in electronic form +from IEEE Std 1003.1-2017, Standard for Information Technology +-- Portable Operating System Interface (POSIX), The Open Group Base +Specifications Issue 7, 2018 Edition, +Copyright (C) 2018 by the Institute of +Electrical and Electronics Engineers, Inc and The Open Group. +In the event of any discrepancy between this version and the original IEEE and +The Open Group Standard, the original IEEE and The Open Group Standard +is the referee document. The original Standard can be obtained online at +http://www.opengroup.org/unix/online.html . +.PP +Any typographical or formatting errors that appear +in this page are most likely +to have been introduced during the conversion of the source files to +man page format. To report such errors, see +https://www.kernel.org/doc/man-pages/reporting_bugs.html . |