ARM Compiler toolchain Using the Linker - ARM Information Center

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Image structure and generation 4.23 How the linker performs library searching, selection, and scanning 4.23.1 See also The linker always searches user libraries before the ARM libraries. If you specify the --no_scanlib command-line option, the linker does not search for the default ARM libraries and uses only those libraries that are specified in the input file list to resolve references. The linker creates an internal list of libraries as follows: 1. Any libraries explicitly specified in the input file list are added to the list. 2. The user-specified search path is examined to identify ARM standard libraries to satisfy requests embedded in the input objects. The best-suited library variants are chosen from the searched directories and their subdirectories. Libraries supplied by ARM have multiple variants that are named according to the attributes of their members. Be aware of the following differences between the way the linker adds object files to the image and the way it adds libraries to the image: • Each object file in the input list is added to the output image unconditionally, whether or not anything refers to it. At least one object must be specified. • A member from a library is included in the output only if: — an object file or an already-included library member makes a non-weak reference to it — the linker is explicitly instructed to add it. Note If a library member is explicitly requested in the input file list, the member is loaded even if it does not resolve any current references. In this case, an explicitly requested member is treated as if it is an ordinary object. Unresolved references to weak symbols do not cause library members to be loaded. Tasks • About weak references and definitions on page 4-32 • Controlling how the linker searches for the ARM standard libraries on page 4-36. Reference Linker Reference: • --keep=section_id on page 2-89 • --remove, --no_remove on page 2-134 • --scanlib, --no_scanlib on page 2-141. ARM DUI 0474C Copyright © 2010-2011 ARM. All rights reserved. 4-35 ID080411 Non-Confidential
Image structure and generation 4.24 Controlling how the linker searches for the ARM standard libraries You can control how the linker searches for the ARM standard libraries with the ARMCC41LIB environment variable or the --libpath command-line option. Some libraries are stored in subdirectories. If the compiler requires a library from a particular subdirectory, it adds an import of a special symbol to identify the subdirectory to the linker. The names of subdirectories are placed in each compiled object by using a symbol of the form Lib$$Request$$sub_dir_name. 4.24.1 Using the --libpath command-line option Use the --libpath command-line option with a comma-separated list of parent directories. This list must end with the parent directory of the ARM library directories armlib and cpplib. The ARMCC41LIB environment variable holds this path. The linker searches subdirectories given by the symbol Lib$$Request$$sub_dir_name, if you include the path separator character on the end of the library path: • \ on Windows • / on Red Hat Linux. For example, for --libpath=mylibs\ and the symbol Lib$$Request$$armlib the linker searches the directories: mylibs mylibs\armlib Note When the linker command-line option --libpath is used, the paths specified by the ARMCC41LIB variable are not searched. The sequential nature of the search ensures that the linker chooses the library that appears earlier in the list if two or more libraries define the same symbol. 4.24.2 Using the ARMCC41LIB or ARMLIB environment variable You can use either of the ARMLIB or ARMCC41LIB environment variables to specify a library path. ARMCC41LIB is the default. The linker searches subdirectories given by the symbol Lib$$Request$$sub_dir_name, if you include the path separator character on the end of the path specified in ARMCC41LIB: • \ on Windows • / on Red Hat Linux. For example, if ARMCC41LIB is set to install_directory\...\lib\, the linker searches the directories: lib lib\armlib lib\cpplib 4.24.3 Library search order The linker searches for libraries in the following order: 1. Relative to the current path. 2. At the location specified with the command-line option --libpath. ARM DUI 0474C Copyright © 2010-2011 ARM. All rights reserved. 4-36 ID080411 Non-Confidential
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® ARM Copyright © 2010-2011 ARM.
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Contents ARM Compiler toolchain Usi
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Contents 7.15 Creating a symdefs fi
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Chapter 1 Conventions and feedback
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Chapter 2 Overview of the linker Th
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Concepts • Demand paging on page
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Page 15 and 16: • --keep_protected_symbols on pag
Page 17 and 18: • --eager_load_debug, --no_eager_
Page 19 and 20: 2.5 What the linker outputs 2.5.1 S
Page 21 and 22: Chapter 3 Linking models supported
Page 23 and 24: 3.2 Bare-metal linking model 3.2.1
Page 25 and 26: Linking models supported by armlink
Page 27 and 28: 3.5.1 See also • There are restri
Page 29 and 30: 3.7 Concepts common to both BPABI a
Page 31 and 32: Image structure and generation •
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Page 37 and 38: 4.4 Methods of specifying an image
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Page 49 and 50: 4.11.2 Example 4.11.3 See also The
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Page 53 and 54: Reference Linker Reference: • --a
Page 55 and 56: 4.16 Overview of veneers 4.16.1 See
Page 57 and 58: 4.18 Veneer types 4.18.1 See also I
Page 59 and 60: 4.20 Reuse of veneers when scatter-
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Page 77 and 78: • --scatter=file on page 2-142. C
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Page 87 and 88: 5.13 Inlining functions with the li
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Page 91 and 92: 5.16 About reordering of tail calli
Page 93 and 94: 5.18 About merging comment sections
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Page 97 and 98: 6.3 Example of using the --info lin
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Page 101 and 102: • Load$$LR$$ load region symbols
Page 103 and 104: 7.2 Accessing linker-defined symbol
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Page 111 and 112: 7.9 Importing linker-defined symbol
Page 113 and 114: 7.11 Section-related symbols 7.11.1
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7.13 Input section symbols 7.13.1 S
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7.15 Creating a symdefs file 7.15.1
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7.17 Reading a symdefs file 7.17.1
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7.18.2 See also 0x0000814D T __argv
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7.20 Specifying steering files on t
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7.22 Steering file format 7.22.1 Se
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7.24 Using $Super$$ and $Sub$$ to p
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Using scatter files • Images with
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8.2 When to use scatter-loading 8.2
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• --startup=symbol, --no_startup
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8.4.1 See also Concepts • About s
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8.5.1 See also } SRAM 0x8000 0x8000
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8.7 Specifying stack and heap using
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8.9 Creating root execution regions
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8.9.2 See also Tasks • Using the
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8.11 Placing functions and data at
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Using scatter files RAM 0x200000 (0
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Using scatter files • Using __at
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Developing Software for ARM ® Proc
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} } .ANY1(+RO) ; evenly distributed
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8.14 Examples of using placement al
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Using scatter files 8.15 Example of
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8.16 Examples of using sorting algo
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8.17 Selecting veneer input section
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Compiler Reference: • __attribute
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8.20 Restrictions on placing __at s
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8.21.1 See also Using scatter files
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8.23 Placing a key in flash memory
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8.25 Placement of sections with ove
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8.25.1 See also Using scatter files
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8.27 Example of placing code in a r
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8.29 Example of placing ARM C++ lib
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8.31 Reserving an empty region Usin
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8.32 About creating regions on page
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8.33 Overalignment of execution reg
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8.35 Expression evaluation in scatt
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8.37 Equivalent scatter-loading des
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Using scatter files Example 8-23 Po
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Using scatter files Example 8-25 Po
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Using scatter files • The ER_ZI e
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Using scatter files Example 8-29 Sc
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Chapter 9 GNU ld script support in
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9.2 Typical use cases for using ld
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Reference Linker Reference: • --l
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9.5 Recommendations for using ld sc
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.data : { __data_start = .; *(.data
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9.6.4 See also .got 0 : { *(.got.pl
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9.7.1 See also } .dynamic : { *(.dy
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9.8.1 See also { *(.bss .bss.*) . =
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Chapter 10 BPABI and SysV shared li
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BPABI and SysV shared libraries and
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10.3 Concepts common to all BPABI m
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10.5 Symbol visibility for BPABI mo
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10.6 Automatic import and export fo
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10.8 Symbol versioning for BPABI mo
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10.10 Linker options for SysV model
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10.13 Addressing modes in the SysV
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10.17 Linker options for bare metal
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10.21 Addressing modes in the BPABI
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10.23 About symbol versioning 10.23
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10.25 Example of creating versioned
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10.27 Linker options for enabling i
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Chapter 11 Features of the Base Pla
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Features of the Base Platform linki
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11.2 Example scatter file for the B
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Features of the Base Platform linki
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