Two Processes Sharing libc | HP UX Software Transition Kit (STK)

is shared by both processes. The total memory requirement for these two processes running simultaneously is 896Kb (256Kb + 128Kb + 512Kb).

Figure 7 Two Processes Sharing libc

Compare this with the memory requirements if prog1 and prog2 are linked with the archive version of libc. As shown in Figure 8 (page 93), 1428Kb of memory is required (768Kb + 640Kb). The numbers in this example are made up, but it is true in general that shared libraries reduce memory requirements.

Figure 8 Two Processes with Their Own Copies of libc

Example Program Comparing Shared and Archive Libraries 93

Image 93

HP UX Software Transition Kit (STK) manual Two Processes Sharing libc

Contents

HP-UX Linker and Libraries Users Guide Page Contents Contents Creating and Using Libraries Linker Tools for Itanium-Based SystemsLinker Tools for PA-RISC Systems Contents Shared Library Management Routines 136 Contents Contents Writing and Generating Position-Independent Code 185 Using Mapfiles 191 Improving Your Application Performance 202 Glossary 225 Intended Audience Document conventions and symbolsRelated Information Document conventions Document Organization HP Encourages Your Comments Improving Your Application Performance Using Mapfiles Compiling Programs on HP-UX An Example OverviewThis chapter addresses the following Compiling Programs on HP-UX An Example Looking Inside a Compiler What is an Object File? Local Definitions Compiler-Linker InteractionGlobal Definitions External References Cc Entering Link editor Crt0.o Startup File Linking Programs on HP-UX Magic Numbers PA-RISC only A.out FilePrograms Entry Point Linker uses four startup files Library Naming Conventions Default Libraries Link Order 32-bit Mode Magic Number Linker OptionsLinking with Libraries File Permissions Default Library Search Path Default LibrariesLibrary Naming Conventions Link Order Running the Program Deferred Binding is the DefaultLoading Programs exec Binding Routines to a Program Linker Thread-Safe Features Determining How to Link Programs or Libraries Linker Tasks Using the Compiler to Link Changing the Default Library Search Path with -Wl, -LExample Using -Wl, -L Example Using -Wl Passing Linker Options from the Compiler Command with -WlGetting Verbose Output with Renaming the Output File with -o Suppressing the Link-Edit Phase with -c Using Linker CommandsLinking with the crt0.o Startup File in 32-bit mode PA-RISC Overriding the Default Linker Search Path with Lpath Using $ORIGIN Augmenting the Default Linker Search Path with -LAugmenting the Default Linker Search Path with +origin Example Using -B immediate Changing the Default Shared Library Binding with -BNonfatal Shared Library Binding with -B nonfatal Restricted Shared Library Binding with -B restricted Shared Library Binding with -B group Direct Shared Library Binding with -B directLazydirect Shared Library Binding with -B lazydirect Shared Library Binding with -B nodelete Example Using -B symbolic Improving Shared Library Performance with -B symbolicComparing -B symbolic with -h and +e Case 1 Building a Shared Library with -B symbolic Symbol Hidden in a Shared Library Or export the convertrtn symbol Example Using -a Option Settings to -aChoosing Archive or Shared Libraries with -a Linking Shared Libraries with -dynamic Example Using +e Exporting Symbols with +eWhen to use -h versus +e Linking Archived Libraries with -noshared Exporting Symbols with +ee Exporting Symbols from main with -EEmitting debug information in a separate file Hiding Symbols with -h Hiding Symbols from Export with +hideallsymbolsExample Using -h Tips on Using -h Hiding and Exporting Symbols When Building a Shared Library Hiding Symbols when Combining .o Files with the -r OptionHiding and Exporting Symbols when Creating an a.out File Moving Libraries after Linking with +b Not Recording Link Time Paths with +nodefaultrapthSpecifying a Path List with +b Syntax of the +b option is Path List Ignoring Dynamic Path Environment Variables with +noenvvar Moving Libraries After Linking with +s and ShlibpathSpecifying a Path List with +s and Shlibpath For more information Path List Controlling Archive Library Loading with +noforceload Thereafter, the following commands would be equivalentPassing Linker Options in a file with -c Passing Linker Options with Ldopts Using the -l option Flagging Unsatisfied Symbols with +noallowunsatsExample Using -l Specifying Libraries with -l and -l Using the IPF Linker with +compat or +std Using the Linker with +compat for Compatibility ModeControlling Output from the Unwind Table with +strip unwind Dynamicflag is passed to shlload Using the Linker with +std for Standard Mode Linking in PA-32 Mode with +compat Linking in PA-64 Mode with +stdChanging Mapfiles with -k and +nodefaultmap Selecting Verbose Output with +vtype All Creating read-only text segment in Mpas executable Turning on the linkage table protection with +protectAllocating Storage for Uninitialized Data with +nobss Initializing Floating Point Environment with +FP Flags that are supported Turn Off Linker Warnings with -w Linker toolset for Itanium-Based systems Changing a Programs Attributes with chatr1Options to change various attributes Libname Immediate +as modeDeferred +b flag +protect disable Enabledisable+md flag +memcheck Viewing Symbols in an Object file with nm1 Format Viewing the Contents of an Object File with elfdump1 +linkmapbss +linkmap+linkmapfile +objdebug Symbol Symbol resolution problems to stderrViewing Library Dependencies with ldd1 +T num2 Listing Dynamic Libraries with pldd1 Example 3 Using the ldd command Options to view information specified files Printing a Stack Trace with pstack1Level with level Parameter Example 6 Calling pstack with -level option Example 5 Calling pstack with a process id Linker Tools for Itanium-Based Systems Viewing the Size of Object File Elements with size1 Reducing Storage Space with strip1Example 9 Calling pstack with special argument Options to control the amount of information stripped Improving Program Start-up with fastbind1 Finding Object Library Ordering Relationships with lorder1 Tracing Inter-Module Procedure Calls with ltrace1Example 10 Example Example 11 Examples $/usr/ccs/bin/ltrace ./a.out -a arg1 arg2 arg3 .. argn Using chatr for 32-bit Program Attributes For the 32-bit compatible syntax Using chatr for 64-bit Program Attributes +dz For the 64-bit only syntax+si +sa $THISSHORTBSS$ Example 12 Viewing Symbols in an Object file with nm1 To view Optional list of symbol resolution problems to stderr Example 13 Viewing library dependencies with ldd1 To display Before you ran fastbind on it Example 14 Improving Program Start-up with fastbind1 $ ar cr library `lorder *.o tsort` ELF Object File Format PA-RISC Changes in Hardware Compatibility PA-RISC 2.0 Compatibility PA-RISC Architectures and Their System ModelsVersions of PA-RISC architecture +nosrcpos +objdebug mode PA64 Mode Linker Options Linker-Defined SymbolsThis section describes the PA64 mode linker options Dynamic Path Searching for Shared Libraries Symbol names Runpath Perform 32-bit link PA-64, IPF 64-bit mode example Symbol Searching in Dependent Libraries System Libraries Locations and Library Name Extension System Library LocationShared Library Extension suffix Statically-bound programs archive-bound programs Overview of Shared and Archive Libraries Using Libraries on HP-UXCreating Libraries on HP-UX Creating Archive Libraries Creating Shared Libraries Out files What are Archive Libraries? Default Behavior When Searching for Libraries at Run Time What are Shared Libraries?Dynamic Loader Running setuid Programs Example Program Comparing Shared and Archive Libraries Two Processes Sharing libc Profiling Shared Libraries with gprof1 Creating Archive Libraries Overview of Creating an Archive Library Contents of an Archive File Example of Creating an Archive Library Replacing, Adding, and Deleting an Object Module Summary of Keys to the ar1 CommandReplacing or Adding an Object Module Deleting an Object Module Using /usr/local/lib or /usr/contrib/lib Using /usr/lib and /usr/lib/pa2064Creating Shared Libraries Archive Library Location IPF Creating Position-Independent Code PIC Example Using +zCreating the Shared Library with ld Comparing +z and +Z Order in Which Libraries are Loaded Load Graph Shared Library Dependencies LibD Placing Loaded Libraries in the Search List Shared Library Location IPF Updating a Shared LibraryImproving Shared Library Performance Incompatible Changes to a Shared Library Consider a case where a.out has the following dependents That is, a.out is built with commands like theseLdpreload Example Symbol resolution order for the user libraries is Ldpreload Example PA-RISCBit Behavior Out -- libA.sl -- libC.sl -- libD.sl -- libB.sl Using Profile-Based Optimization on Shared Libraries Exporting Only the Required SymbolsPlacing Frequently-Called Routines Together Making Shared Libraries Non-Writable Using the +ESlit/+Olit=all Option to ccY.o None +condrodata Command-Line Option Using Filtered Shared Libraries 32-bit Mode OnlyBuilding Filtered Shared Libraries Initializers Run time behavior of filtered shared libraries When to Use Shared Library Versioning Version Control with Shared LibrariesFunction Level Versioning How to Use Library-Level Versioning Maintaining Old Versions of Library ModulesLibrary-Level Versioning File System Links to Shared Libraries Creating a New, Incompatible Version of the Library+h Option and Internal Names Then set up the corresponding file system links Using shlload3X with Library-Level VersioningIntra-Library Versioning PA-RISC only Version Number Compiler Directive Adding New Versions to a Shared Library Shared Library Dependencies and Version Control#pragma Hpshlibversion date $SHLIBVERSION date Switching from Archive to Shared Libraries Relying on Undocumented Linker BehaviorSpecifying a Version Date Stack Usage Absolute Virtual AddressesVersion Control Debugger Limitations Using the chroot Command with Shared Libraries Summary of HP-UX LibrariesProfiling Limitations Example 1 Unsatisfied Symbols Compiling Example 1 Unsatisfied Symbols Example 1 Unsatisfied Symbols Modifying a Function Example 1 Unsatisfied Symbols Creating the Executable Example 1 Unsatisfied Symbols Problem of Unsatisfied Symbol Example 2 Using shlload3X Example 2 Using shlload3X Creating the Executable Example 3 Hidden Definitions Example 2 Using shlload3X Rebuilding the Shared Library Example 3 Hidden Definitions Compiling Example 3 Hidden Definitions Modifying a Function Using Shared Libraries in Default Mode Dthpneeded entry Internal Name Processing Shared Library Symbol Binding Semantics Link-Time Symbol Resolution in Shared LibrariesDynamic Path Searching for Shared Libraries Resolution of Unsatisfied Shared Library References If these files are compiled and linked asPA-32 linker toolset produces Promotion of Uninitialized Global Data Items Symbol Searching in Dependent Libraries Search Order of Dependent Libraries Mixed Mode Shared Libraries Libfile4.so IPF Library Examples Library example IPF Dynamic Path Searching Following example builds a standard mode library Library Example IPF Compatibility Mode Link You can use chatr+s to enable a.out in file1 and file2For the following libraries with dependencies Linking Libraries with +b pathlist Linker issues the following error message When linking main.o, the link order is 1. ./libbar.so foundAbove example, if you type Instead Dlopen Routines Summary Shared Library Management Routine SummariesDo not mix use of the shlload and dlopen APIs Dl* routines for shared library management Shared Library Header Files Related Files and CommandsShlload Routine Summary Routines for shared library management Initializers for Shared Libraries Using Shared Libraries with cc and ld OptionsStyles of Initializers Init/Fini Style Initializers Using Init/Fini Initializers HP-UX-10.X Style InitializersInit and Fini Usage Example Source for lib1.so file lib1.c lib1 Finis from any .o files used in my64bit.a Ordering Within an Executable or Shared Library Ordering Among Executables and Shared Libraries Using HP-UX 10.X Style Initializers Declaring the Initializer with the +I OptionOrder of Execution of Multiple Initializers Accessing Initializers Addresses Initializer SyntaxExample An Initializer for Each Library Source for testlib.c #include stdio.h #include dl.h main Source for Initializer file init.c #include dl.h Example a Common Initializer for Multiple Libraries Following are the commands used to build these libraries Dlopen Shared Library Management Routines Following is the command to create the executable testlib2Dlopen Routine Syntax Parameters Return Values Description Dlopen Shared Library Management Routines Using dlopen to load a shared library Synopsis Dlsetlibpath Routine Using dlsetlibpath to set the dynamic search path Rtldflagdisablestdpath Rtldflagdisablecwdpath Dlerrno Routine ErrorsDlgetfileinfo Routine Multithread Usage Shared Library Management Routines Dlerror Routine Using dlerror to get diagnostic informationDlsym Routine Handle Usage Index Dlget RoutineDesc Descsize Dlmodinfo Routine Using dlget to retrieve information about loaded modules Dlgetname Routine Using dlmodinfo to retrieve information about a load module Dlclose Routine Using dlgetname to retrieve pathnameDlclose routine closes a shared library Int dlclosevoid *handle Using dlclose to unload a shared library Dladdr routine gets the symbolic information for an addressDladdr Routine Diagnostics Using dladdr to get the symbolic information for an address Following example shows how to use dladdr toDlmodadd Routine Dlmodremove removes information registered using dlmodadd Dlmodremove RoutineDlgetmodinfo Routine Following example shows how to use dlgetmodinfo Using dlgetmodinfo Shlload Routine Shlload Shared Library Management RoutinesParameters Shlload routine explicitly loads a library Enomem Shlload Usage Shlload ExampleLoadlib Function to Load a Shared Library Bindverbose Modifier Bindnonfatal ModifierBindfirst Modifier Dynamicpath Modifier Shlfindsym Routine LibG together and correctly resolves all symbolsBindtogether Modifier Bindbreadthfirst Modifier Handle = Null Shlt handleShlfindsym&handle,foo Same as Typedata Shlfindsym Example Index Shlget and shlgetr Routines Example Shldefinesym Routine Shlgethandle and shlgethandler Routines Shlgetsymbols Routine Typeprocedure Showsymbols Display Shared Library Symbols Shlsymbol StructureMembers of the shlsymbol structure are defined as follows Example 17 shlgetsymbols Example Showall Use showsymbols to Show All Symbols Showall program shown above was compiled with the commandOutput produced by running this program is shown below Fpumodelstorage Shlunload Routine Unsupported Shared Library Management Routines Dynamic Loader Compatibility WarningsUnsupported Shared Library Management Flags Shlunload Routine Returning Etxtbsy Typeprocedure Typedata Typestorage What is a Absolute Object Code? What is a Relocatable Object Code? Generating Position-Independent Code What is a Position-Independent Code? PIC Requirements for Compilers and Assembly Code Long Calls Long Branches and Switch TablesAssigned Goto Statements Literal References Global and Static Variable References Procedure Labels Writing and Generating Position-Independent Code Changing Mapfiles with -k filename and +nodefaultmap Mapfile Example Using -k mapfile and +nodefaultmapControlling Mapfiles with the -k Option Using Mapfiles IPF 32-bit linker uses the following default mapfile Default HP-UX 11.0 Release MapfileSimple Mapfile Following directives show how a simple mapfile would appear Using Mapfiles Defining Syntax for Mapfile Directives Segment Flags Defining Mapfile Segment DeclarationsAttributes and their values Segment declarations support the following segment flags Defining Mapfile Section Mapping Directives Mapfile Segment Declaration ExamplesSection attributes and their valid values are as follows Placement of Segments in an Executable Internal Map StructureMapping Input Sections to Segments Map Structure Fatal Errors Mapfile Option Error Messages Mapfile Option Error Messages Invoking Linker Optimizations from the Compile Line Linker Optimizations Unused Procedure Elimination with +Oprocelim Incompatibilities with other OptionsComplete Executables Profile-Based Optimization PA-RISC Using PBO When to Use PBOHow to Use PBO Instrumenting +I/-I Startup File icrt0.o -I Linker OptionCode Generation from I-SOMs Building Portable Code with Linker Optimization Profiling Storing Profile Information for Multiple Programs -P Linker Option Optimizing Based on Profile Data +P/-P Specifying a Different flow.data File with +df Using The flow.data FileSpecifying a Different flow.data with Flowdata Interaction between Flowdata and +df Selecting an Optimization Level with PBO Using PBO to Optimize Shared Libraries Using PBO with ld -r Restrictions and Limitations of PBO Size Essentially empty Compatibility with 9.0 PBO Profile-Based Optimization Itanium Options to Improve TLB Hit RatesIncremental Linking Example 19 Examples Any of the padding spaces have been exhausted Archive Library Processing Using Incremental Linking OptionsShared Library Processing Performance Improving Performance with the Global Symbol Table Reusing Compiled Object Files PA-RISC Improving Performance by Optimizing the Hash Table Size Using fastbind Improving Performance with Function Symbol AliasingImproving Shared Library Start-Up Time with fastbind Example 20 Example Invoking the fastbind Tool How to Tell if fastbind Information is CurrentInvoking fastbind from the Linker Example 21 Example Turning off fastbind at Run Time Removing fastbind Information from a FileExample 22 Example See the fastbind1 man Glossary SOM PBO Rpath