Note: This is a draft readme.
This is a preview release of ICU. It is not recommended for production use.
This is a release candidate version of ICU4C. It is not recommended for production use.
Last updated: 2020-Dec-02
Copyright © 2016 and later: Unicode, Inc. and others. License & terms of use:
http://www.unicode.org/copyright.html
Copyright © 1997-2016 International Business Machines Corporation and others.
All Rights Reserved.
Today's software market is a global one in which it is desirable to develop and maintain one application (single source/single binary) that supports a wide variety of languages. The International Components for Unicode (ICU) libraries provide robust and full-featured Unicode services on a wide variety of platforms to help this design goal. The ICU libraries provide support for:
ICU has a sister project ICU4J that extends the internationalization capabilities of Java to a level similar to ICU. The ICU C/C++ project is also called ICU4C when a distinction is necessary.
This document describes how to build and install ICU on your machine. For
other information about ICU please see the following table of links.
The ICU homepage also links to related information about writing
internationalized software.
| ICU, ICU4C & ICU4J Homepage | http://icu-project.org/ |
| FAQ - Frequently Asked Questions about ICU | https://unicode-org.github.io/icu/userguide/icufaq |
| ICU User's Guide | https://unicode-org.github.io/icu/userguide/ |
| How To Use ICU | https://unicode-org.github.io/icu/userguide/howtouseicu |
| Download ICU Releases | http://site.icu-project.org/download |
| ICU4C API Documentation Online | http://icu-project.org/apiref/icu4c/ |
| Online ICU Demos | http://demo.icu-project.org/icu-bin/icudemos |
| Contacts and Bug Reports/Feature Requests | http://site.icu-project.org/contacts |
Important: Please make sure you understand the Copyright and License Information.
See the ICU 68 download page for more information on this release, including any other changes, bug fixes, known issues, changes to supported platforms and build environments, and migration issues for existing applications migrating from previous ICU releases.
See the API Change Report for a complete list of APIs added, removed, or changed in this release.
For changes in previous releases, see the main ICU download page with its version-specific subpages.
There are two ways to download ICU releases:
In the descriptions below, <ICU> is the full
path name of the ICU directory (the top level directory from the distribution
archives) in your file system. You can also view the ICU Architectural
Design section of the User's Guide to see which libraries you need for
your software product. You need at least the data ([lib]icudt)
and the common ([lib]icuuc) libraries in order to use ICU.
| File | Description |
|---|---|
| readme.html | Describes the International Components for Unicode (this file) |
| LICENSE | Contains the text of the ICU license |
| Directory | Description |
|---|---|
| <ICU>/source/common/ | The core Unicode and support functionality, such as resource bundles, character properties, locales, codepage conversion, normalization, Unicode properties, Locale, and UnicodeString. |
| <ICU>/source/i18n/ | Modules in i18n are generally the more data-driven, that is to say resource bundle driven, components. These deal with higher-level internationalization issues such as formatting, collation, text break analysis, and transliteration. |
| <ICU>/source/layoutex/ | Contains the ICU paragraph layout engine. |
| <ICU>/source/io/ | Contains the ICU I/O library. |
| <ICU>/source/data/ |
This directory contains the source data in text format, which is compiled into binary form during the ICU build process. It contains several subdirectories, in which the data files are grouped by function. Note that the build process must be run again after any changes are made to this directory. If some of the following directories are missing, it's probably because you got an official download. If you need the data source files for customization, then please download the complete ICU source code from the ICU repository.
If you are creating a special ICU build, you can set the ICU_DATA environment variable to the out/ or the out/build/ directories, but this is generally discouraged because most people set it incorrectly. You can view the ICU Data Management section of the ICU User's Guide for details. |
| <ICU>/source/test/intltest/ | A test suite including all C++ APIs. For information about running the test suite, see the build instructions specific to your platform later in this document. |
| <ICU>/source/test/cintltst/ | A test suite written in C, including all C APIs. For information about running the test suite, see the build instructions specific to your platform later in this document. |
| <ICU>/source/test/iotest/ | A test suite written in C and C++ to test the icuio library. For information about running the test suite, see the build instructions specific to your platform later in this document. |
| <ICU>/source/test/testdata/ | Source text files for data, which are read by the tests. It contains the subdirectories out/build/ which is used for intermediate files, and out/ which contains testdata.dat. |
| <ICU>/source/tools/ | Tools for generating the data files. Data files are generated by invoking <ICU>/source/data/build/makedata.bat on Win32 or <ICU>/source/make on UNIX. |
| <ICU>/source/samples/ | Various sample programs that use ICU |
| <ICU>/source/extra/ | Non-supported API additions. Currently, it contains the 'uconv' tool to perform codepage conversion on files. |
| <ICU>/packaging/ | This directory contain scripts and tools for packaging the final ICU build for various release platforms. |
| <ICU>/source/config/ | Contains helper makefiles for platform specific build commands. Used by 'configure'. |
| <ICU>/source/allinone/ | Contains top-level ICU workspace and project files, for instance to build all of ICU under one MSVC project. |
| <ICU>/include/ | Contains the headers needed for developing software that uses ICU on Windows. |
| <ICU>/lib/ | Contains the import libraries for linking ICU into your Windows application. |
| <ICU>/bin/ | Contains the libraries and executables for using ICU on Windows. |
Depending on the platform and the type of installation, we recommend a small number of modifications and build options. Note that C99 compatibility is now required.
icu::UnicodeString,
or do using icu::UnicodeString; where appropriate.
If your code relies on the "using namespace icu;" that used to be in unicode/uversion.h,
then you need to update your code.-DU_USING_ICU_NAMESPACE=1
or by modifying unicode/uversion.h:
Index: icu4c/source/common/unicode/uversion.h
===================================================================
--- icu4c/source/common/unicode/uversion.h (revision 40704)
+++ icu4c/source/common/unicode/uversion.h (working copy)
@@ -127,7 +127,7 @@
defined(U_LAYOUTEX_IMPLEMENTATION) || defined(U_TOOLUTIL_IMPLEMENTATION)
# define U_USING_ICU_NAMESPACE 0
# else
-# define U_USING_ICU_NAMESPACE 0
+# define U_USING_ICU_NAMESPACE 1
# endif
# endif
# if U_USING_ICU_NAMESPACE
-DU_USING_ICU_NAMESPACE=0
or by modifying unicode/uversion.h:
Index: source/common/unicode/uversion.h
===================================================================
--- source/common/unicode/uversion.h (revision 26606)
+++ source/common/unicode/uversion.h (working copy)
@@ -180,7 +180,8 @@
# define U_NAMESPACE_QUALIFIER U_ICU_NAMESPACE::
# ifndef U_USING_ICU_NAMESPACE
-# define U_USING_ICU_NAMESPACE 1
+ // Set to 0 to force namespace declarations in ICU usage.
+# define U_USING_ICU_NAMESPACE 0
# endif
# if U_USING_ICU_NAMESPACE
U_NAMESPACE_USE
ICU call sites then either qualify ICU types explicitly,
for example icu::UnicodeString,
or do using icu::UnicodeString; where appropriate.-DU_CHARSET_IS_UTF8=1 or
modify unicode/utypes.h (in ICU 4.8 and below)
or modify unicode/platform.h (in ICU 49 and higher):
Index: source/common/unicode/utypes.h =================================================================== --- source/common/unicode/utypes.h (revision 26606) +++ source/common/unicode/utypes.h (working copy) @@ -160,7 +160,7 @@ * @see UCONFIG_NO_CONVERSION */ #ifndef U_CHARSET_IS_UTF8 -# define U_CHARSET_IS_UTF8 0 +# define U_CHARSET_IS_UTF8 1 #endif /*===========================================================================*/
UnicodeString
with a single character by using an integer,
and it can lead to inadvertent dependency on the conversion framework
by using a C string literal.UChar
and from-UChar32 constructors explicit via
-DUNISTR_FROM_CHAR_EXPLICIT=explicit or similar.const char* and
from-const UChar* constructors explicit via
-DUNISTR_FROM_STRING_EXPLICIT=explicit or similar.U_NO_DEFAULT_INCLUDE_UTF_HEADERS to 1
(via -D or uconfig.h, as above)
and include those header files explicitly that you actually need.U_HIDE_OBSOLETE_UTF_OLD_H to 1
(via -D or uconfig.h, as above).
Use of any of these macros should be replaced as noted
in the comments for the obsolete macro.u_setDataDirectory())
or with a pointer to the data (udata_setCommonData())
before other ICU API calls.
This is usually easy if ICU is used from an application where
main() takes care of such initialization.
It may be hard if ICU is shipped with
another shared library (such as the Xerces-C++ XML parser)
which does not control main().--with-data-packaging=archive
on the configure command line, as inrunConfigureICU Linux --with-data-packaging=archiverunConfigureICU Linux --enable-static --disable-shared~/icu$ git clone export https://github.com/unicode-org/icu.git ~/icu$ mkdir icu4c-build ~/icu$ cd icu4c-build ~/icu/icu4c-build$ ../icu/icu4c/source/runConfigureICU Linux ~/icu/icu4c-build$ make check
runConfigureICU. If you experience difficulty,
try using an absolute path to runConfigureICU
instead.)
If ICU is installed as a system-level library, there are further opportunities and restrictions to consider. For details, see the Using ICU as an Operating System Level Library section of the User Guide ICU Architectural Design chapter.
-DICU_DATA_DIR=/path/to/icu/data
when building the ICU code. (Used by source/common/putil.c.)-DICU_NO_USER_DATA_OVERRIDE
if you do not want the "ICU_DATA" environment variable to be used.
(An application can still override the data path via
u_setDataDirectory() or
udata_setCommonData().@draft
is new and not yet stable. Applications must not rely on unstable
APIs from a system-level library.
Define U_HIDE_DRAFT_API, U_HIDE_INTERNAL_API
and U_HIDE_SYSTEM_API
by modifying unicode/utypes.h before installing it.\brief C++ API.
Consider not installing these header files, or define U_SHOW_CPLUSPLUS_API
to be 0 by modifying unicode/utypes.h before installing it.runConfigureICU Linux --disable-renamingICU4C can be customized via a number of user-configurable settings.
Many of them are controlled by preprocessor macros which are
defined in the source/common/unicode/uconfig.h header file.
Some turn off parts of ICU, for example conversion or collation,
trading off a smaller library for reduced functionality.
Other settings are recommended (see previous section)
but their default values are set for better source code compatibility.
In order to change such user-configurable settings, you can
either modify the uconfig.h header file by adding
a specific #define ... for one or more of the macros
before they are first tested,
or set the compiler's preprocessor flags (CPPFLAGS) to include
an equivalent -D macro definition.
Building International Components for Unicode requires:
Cygwin is required if using a version of MSVC other than the one compatible with the supplied project files or if other compilers are used to build ICU. (e.g. GCC)
The steps are:
Building with other versions of Visual Studio Note:
The particular version of the MSVC compiler tool-set (and thus the corresponding version of Visual Studio) that
is used to compile ICU is determined by the "PlatformToolset" property. This property is stored in two
different shared files that are used to set common configuration settings amongst the various ICU "*.vcxproj" project files.
For the non-UWP projects, this setting is in the shared file called "Build.Windows.ProjectConfiguration.props" located
in the "allinone" directory.
For the UWP projects, this setting is in the shared file called "Build.Windows.UWP.ProjectConfiguration.props", also
located in the "allinone" directory.
The value of v140 corresponds to the Visual Studio 2015 compiler tool set, whereas the value of
v141 corresponds to the Visual Studio 2017 compiler tool set.
In order to build the non-UWP projects with Visual Studio 2015 you will need to modify the file
called "Build.Windows.ProjectConfiguration.props" to change the value of the PlatformToolset property.
Note however that Visual Studio 2017 is required for building the UWP projects.
Please consider: Using older versions of the MSVC compiler is generally not recommended due to the improved support for the C++11 standard in newer versions of the compiler.
Re-targeting the Windows 10 SDK for the UWP projects Note: If the version of the Windows 10 SDK that you have installed does not match the version used by the UWP projects, then you will need to "retarget" them to use the version of the SDK that you have installed instead. There are two ways to do this:
Using MSBUILD At The Command Line Note: You can build ICU from the command line instead of using the Visual Studio GUI. Assuming that you have properly installed Visual Studio to support command line building, you should have a shortcut for the "Developer Command Prompt" listed in the Start Menu. (For Visual Studio 2017 you will need to install the "Desktop development with C++" option).
'msbuild source\allinone\allinone.sln /p:Configuration=Debug /p:Platform=Win32'.'msbuild source\allinone\allinone.sln /p:Configuration=Release /p:Platform=x64'.'devenv.com source\allinone\allinone.sln /build "Debug|Win32"'.'devenv.com source\allinone\allinone.sln /build "Release|x64"'.Skipping the UWP Projects on the Command Line Note:
You can skip (or omit) building the UWP projects on the command line by passing the argument
'SkipUWP=true' to either MSBUILD or devenv.
'msbuild source\allinone\allinone.sln /p:Configuration=Debug /p:Platform=Win32 /p:SkipUWP=true'.'msbuild source\allinone\allinone.sln /p:Configuration=Release /p:Platform=x64 /p:SkipUWP=true'.You can also use Cygwin with the MSVC compiler to build ICU, and you can refer to the How To Build And Install On Windows with Cygwin section for more details.
Setting Active Platform Note: Even though you are able to select "x64" as the active platform, if your operating system is not a 64 bit version of Windows, the build will fail. To set the active platform, two different possibilities are:
Setting Active Configuration Note: To set the active configuration, two different possibilities are:
Batch Configuration Note: If you want to build the Win32 and x64 platforms and Debug and Release configurations at the same time, choose "Build" menu, and select "Batch Build...". Click the "Select All" button, and then click the "Rebuild" button.
Building International Components for Unicode with this configuration requires:
There are two ways you can build ICU with Cygwin. You can build with gcc or Microsoft Visual C++. If you use gcc, the resulting libraries and tools will depend on the Cygwin environment. If you use Microsoft Visual C++, the resulting libraries and tools do not depend on Cygwin and can be more easily distributed to other Windows computers (the generated man pages and shell scripts still need Cygwin). To build with gcc, please follow the "How To Build And Install On UNIX" instructions, while you are inside a Cygwin bash shell. To build with Microsoft Visual C++, please use the following instructions:
Configuring ICU on Windows NOTE:
Ensure that the order of the PATH is MSVC, Cygwin, and then other PATHs. The configure script needs certain tools in Cygwin (e.g. grep).
Also, you may need to run "dos2unix.exe" on all of the scripts (e.g. configure) in the top source directory of ICU. To avoid this issue, you can download the ICU source for Unix platforms (icu-xxx.tgz).
In addition to the Unix configuration note the following configure options currently do not work on Windows with Microsoft's compiler. Some options can work by manually editing icu/source/common/unicode/pwin32.h, but manually editing the files is not recommended.
Building International Components for Unicode on UNIX requires:
Here are the steps to build ICU:
icu/source.
cd icu/source
make if GNU make is the default make on
your platform) to compile the libraries and all the data files. The proper
name of the GNU make command is printed at the end of the configuration
run, as in "You must use gmake to compile ICU".
Configuring ICU NOTE: Type "./runConfigureICU --help" for help on how to run it and a list of supported platforms. You may also want to type "./configure --help" to print the available configure options that you may want to give runConfigureICU. If you are not using the runConfigureICU script, or your platform is not supported by the script, you may need to set your CC, CXX, CFLAGS and CXXFLAGS environment variables, and type "./configure". HP-UX users, please see this note regarding HP-UX multithreaded build issues with newer compilers. Solaris users, please see this note regarding Solaris multithreaded build issues.
ICU is built with strict compiler warnings enabled by default. If this causes excessive numbers of warnings on your platform, use the --disable-strict option to configure to reduce the warning level.
Running The Tests From The Command Line NOTE: You may have to set certain variables if you with to run test programs individually, that is apart from "gmake check". The environment variable ICU_DATA can be set to the full pathname of the data directory to indicate where the locale data files and conversion mapping tables are when you are not using the shared library (e.g. by using the .dat archive or the individual data files). The trailing "/" is required after the directory name (e.g. "$Root/source/data/out/" will work, but the value "$Root/source/data/out" is not acceptable). You do not need to set ICU_DATA if the complete shared data library is in your library path.
Installing ICU NOTE: Some platforms use package management tools to control the installation and uninstallation of files on the system, as well as the integrity of the system configuration. You may want to check if ICU can be packaged for your package management tools by looking into the "packaging" directory. (Please note that if you are using a snapshot of ICU from Git, it is probable that the packaging scripts or related files are not up to date with the contents of ICU at this time, so use them with caution).
You can install ICU on z/OS or OS/390 (the previous name of z/OS), but IBM tests only the z/OS installation. You install ICU in a z/OS UNIX system services file system such as HFS or zFS. On this platform, it is important that you understand a few details:
OS390_XPLINK=1 prior to
invoking the make process to produce binaries that are enabled for
XPLINK. The XPLINK option, which is available for z/OS 1.2 and later,
requires the PTF PQ69418 to build XPLINK enabled binaries.export _CXX_PSYSIX="CEE.SCEELIB(C128N)":"CBC.SCLBSID(IOSTREAM,COMPLEX)"
export _CEE_RUNOPTS="HEAPPOOLS(ON),HEAP(4M,1M,ANY,FREE,0K,4080)"
By default, ICU builds its libraries into the UNIX file system (HFS). In addition, there is a z/OS specific environment variable (OS390BATCH) to build some libraries into the z/OS native file system. This is useful, for example, when your application is externalized via Job Control Language (JCL).
The OS390BATCH environment variable enables non-UNIX support including the batch environment. When OS390BATCH is set, the libicui18nXX.dll, libicuucXX.dll, and libicudtXXe.dll binaries are built into data sets (the native file system). Turning on OS390BATCH does not turn off the normal z/OS UNIX build. This means that the z/OS UNIX (HFS) DLLs will always be created.
Two additional environment variables indicate the names of the z/OS data sets to use. The LOADMOD environment variable identifies the name of the data set that contains the dynamic link libraries (DLLs) and the LOADEXP environment variable identifies the name of the data set that contains the side decks, which are normally the files with the .x suffix in the UNIX file system.
A data set is roughly equivalent to a UNIX or Windows file. For most kinds of data sets the operating system maintains record boundaries. UNIX and Windows files are byte streams. Two kinds of data sets are PDS and PDSE. Each data set of these two types contains a directory. It is like a UNIX directory. Each "file" is called a "member". Each member name is limited to eight bytes, normally EBCDIC.
Here is an example of some environment variables that you can set prior to building ICU:
OS390BATCH=1 LOADMOD=USER.ICU.LOAD LOADEXP=USER.ICU.EXP
The PDS member names for the DLL file names are as follows:
IXMIXXIN --> libicui18nXX.dll IXMIXXUC --> libicuucXX.dll IXMIXXDA --> libicudtXXe.dll
You should point the LOADMOD environment variable at a partitioned data set extended (PDSE) and point the LOADEXP environment variable at a partitioned data set (PDS). The PDSE can be allocated with the following attributes:
Data Set Name . . . : USER.ICU.LOAD Management class. . : **None** Storage class . . . : BASE Volume serial . . . : TSO007 Device type . . . . : 3390 Data class. . . . . : LOAD Organization . . . : PO Record format . . . : U Record length . . . : 0 Block size . . . . : 32760 1st extent cylinders: 1 Secondary cylinders : 5 Data set name type : LIBRARY
The PDS can be allocated with the following attributes:
Data Set Name . . . : USER.ICU.EXP Management class. . : **None** Storage class . . . : BASE Volume serial . . . : TSO007 Device type . . . . : 3390 Data class. . . . . : **None** Organization . . . : PO Record format . . . : FB Record length . . . : 80 Block size . . . . : 3200 1st extent cylinders: 3 Secondary cylinders : 3 Data set name type : PDS
Before you start building ICU, ICU requires the following:
The following describes how to setup and build ICU. For background information, you should look at the UNIX build instructions.
CRTLIB LIB(libraryname)
ADDENVVAR ENVVAR(OUTPUTDIR) VALUE('libraryname') REPLACE(*YES)
ADDENVVAR ENVVAR(MAKE) VALUE('gmake') REPLACE(*YES)
CHGJOB CCSID(37)qsh
export PATH=/QIBM/ProdData/DeveloperTools/qsh/bin:$PATH:/QOpenSys/usr/bin
gzip -d icu-X.Y.tgz
unpax-icu.sh icu.tar
cd icu/as_is/os400 qsh bldiculd.sh cd ../../..
cd icu/source ./runConfigureICU IBMi --prefix=/path/to/somewhere --with-data-packaging=archive
gmake
gmake check(The QIBM_MULTI_THREADED=Y flag will be automatically applied to intltest - you can look at the iSeries Information Center for more details regarding the running of multiple threads on IBM i.)
This section will explain how to build ICU on one platform, but to produce binaries intended to run on another. This is commonly known as a cross compile.
Normally, in the course of a build, ICU needs to run the tools that it builds in order to generate and package data and test-data.In a cross compilation setting, ICU is built on a different system from that which it eventually runs on. An example might be, if you are building for a small/headless system (such as an embedded device), or a system where you can't easily run the ICU command line tools (any non-UNIX-like system).
To reduce confusion, we will here refer to the "A" and the "B" system.System "A" is the actual system we will be running on- the only requirements on it is are it is able to build ICU from the command line targetting itself (with configure or runConfigureICU), and secondly, that it also contain the correct toolchain for compiling and linking for the resultant platform, referred to as the "B" system.
The autoconf docs use the term "build" for A, and "host" for B. More details at: http://www.gnu.org/software/autoconf/manual/html_node/Specifying-Names.html
Three initially-empty directories will be used in this example:
| /icu | a copy of the ICU source |
|---|---|
| /buildA | an empty directory, it will contain ICU built for A (MacOSX in this case) |
| /buildB | an empty directory, it will contain ICU built for B (HaikuOS in this case) |
cd /buildA sh /icu/source/runConfigureICU MacOSX gnumake
"--with-cross-build" takes an absolute path.
cd /buildB sh /icu/source/configure --host=i586-pc-haiku --with-cross-build=/buildA gnumake
There are many ways that a person can package ICU with their software products. Usually only the libraries need to be considered for packaging.
On UNIX, you should use "gmake install" to make it easier to develop and package ICU. The bin, lib and include directories are needed to develop applications that use ICU. These directories will be created relative to the "--prefix=dir" configure option (See the UNIX build instructions). When ICU is built on Windows, a similar directory structure is built.
When changes have been made to the standard ICU distribution, it is recommended that at least one of the following guidelines be followed for special packaging.
Following these guidelines prevents other applications that use a standard ICU distribution from conflicting with any libraries that you need. On operating systems that do not have a standard C++ ABI (name mangling) for compilers, it is recommended to do this special packaging anyway. More details on customizing ICU are available in the User's Guide. The ICU Source Code Organization section of this readme.html gives a more complete description of the libraries.
| Library Name | Windows Filename | Linux Filename | Comment |
|---|---|---|---|
| Data Library | icudtXYl.dll | libicudata.so.XY.Z | Data required by the Common and I18n libraries. There are many ways to package and customize this data, but by default this is all you need. |
| Common Library | icuucXY.dll | libicuuc.so.XY.Z | Base library required by all other ICU libraries. |
| Internationalization (i18n) Library | icuinXY.dll | libicui18n.so.XY.Z | A library that contains many locale based internationalization (i18n) functions. |
| Layout Extensions Engine | iculxXY.dll | libiculx.so.XY.Z | An optional engine for doing paragraph layout that uses parts of ICU. HarfBuzz is required. |
| ICU I/O (Unicode stdio) Library | icuioXY.dll | libicuio.so.XY.Z | An optional library that provides a stdio like API with Unicode support. |
| Tool Utility Library | icutuXY.dll | libicutu.so.XY.Z | An internal library that contains internal APIs that are only used by ICU's tools. If you do not use ICU's tools, you do not need this library. |
Normally only the above ICU libraries need to be considered for packaging. The versionless symbolic links to these libraries are only needed for easier development. The X, Y and Z parts of the name are the version numbers of ICU. For example, ICU 2.0.2 would have the name libicuuc.so.20.2 for the common library. The exact format of the library names can vary between platforms due to how each platform can handles library versioning.
Some versions of ICU require calling the u_init() function
from uclean.h to ensure that ICU is initialized properly. In
those ICU versions, u_init() must be called before ICU is used
from multiple threads. There is no harm in calling u_init() in a
single-threaded application, on a single-CPU machine, or in other cases where
u_init() is not required.
In addition to ensuring thread safety, u_init() also attempts
to load at least one ICU data file. Assuming that all data files are packaged
together (or are in the same folder in files mode), a failure code from
u_init() usually means that the data cannot be found. In this
case, the data may not be installed properly, or the application may have
failed to call udata_setCommonData() or
u_setDataDirectory() which specify to ICU where it can find its
data.
Since u_init() will load only one or two data files, it
cannot guarantee that all of the data that an application needs is available.
It cannot check for all data files because the set of files is customizable,
and some ICU services work without loading any data at all. An application
should always check for error codes when opening ICU service objects (using
ucnv_open(), ucol_open(), C++ constructors,
etc.).
ICU 3.4 self-initializes properly for multi-threaded use. It achieves this without performance penalty by hardcoding the core Unicode properties data, at the cost of some flexibility. (For details see Jitterbug 4497.)
u_init() can be used to check for data loading. It tries to
load the converter alias table (cnvalias.icu).
These ICU versions require a call to u_init() before
multi-threaded use. The services that are directly affected are those that
don't have a service object and need to be fast: normalization and character
properties.
u_init() loads and initializes the data files for
normalization and character properties (unorm.icu and
uprops.icu) and can therefore also be used to check for data
loading.
ICU 2.4 and earlier versions were not prepared for multithreaded use on
multi-CPU platforms where the CPUs implement weak memory coherency. These
CPUs include: Power4, Power5, Alpha, Itanium. u_init() was not
defined yet.
When ICU is built with aCC on HP-UX, the -AA compiler flag is used. It is required in order to use the latest <iostream> API in a thread safe manner. This compiler flag affects the version of the C++ library being used. Your applications will also need to be compiled with -AA in order to use ICU.
In order to avoid synchronization and threading issues, developers are suggested to strictly follow the compiling and linking guidelines for multithreaded applications, specified in the following SUn Solaris document available from Oracle. Most notably, pay strict attention to the following statements from Sun:
To use libthread, specify -lthread before -lc on the ld command line, or last on the cc command line.
To use libpthread, specify -lpthread before -lc on the ld command line, or last on the cc command line.
Failure to do this may cause spurious lock conflicts, recursive mutex failure, and deadlock.
Source: "Multithreaded Programming Guide, Compiling and
Debugging", Sun Microsystems, 2002
https://docs.oracle.com/cd/E19683-01/806-6867/compile-74765/index.html
Note, a version of that chapter from a 2008 document update covering both Solaris 9
and Solaris 10 is available here:
http://docs.oracle.com/cd/E19253-01/816-5137/compile-94179/index.html
If you are building on the Windows platform, it is important that you understand a few of the following build details.
As delivered, the International Components for Unicode build as several DLLs, which are placed in the "<ICU>\bin64" directory. You must add this directory to the PATH environment variable in your system, or any executables you build will not be able to access International Components for Unicode libraries. Alternatively, you can copy the DLL files into a directory already in your PATH, but we do not recommend this. You can wind up with multiple copies of the DLL and wind up using the wrong one.
Windows 2000/XP and above: Use the System Icon in the Control Panel. Pick the "Advanced" tab. Select the "Environment Variables..." button. Select the variable PATH in the lower box, and select the lower "Edit..." button. In the "Variable Value" box, append the string ";<ICU>\bin64" to the end of the path string. If there is nothing there, just type in "<ICU>\bin64". Click the Set button, then the OK button.
Note: When packaging a Windows application for distribution and installation on user systems, copies of the ICU DLLs should be included with the application, and installed for exclusive use by the application. This is the only way to insure that your application is running with the same version of ICU, built with exactly the same options, that you developed and tested with. Refer to Microsoft's guidelines on the usage of DLLs, or search for the phrase "DLL hell" on msdn.microsoft.com.
If you are building on a UNIX platform, and if you are installing ICU in a non-standard location, you may need to add the location of your ICU libraries to your LD_LIBRARY_PATH or LIBPATH environment variable (or the equivalent runtime library path environment variable for your system). The ICU libraries may not link or load properly without doing this.
Note that if you do not want to have to set this variable, you may instead use the --enable-rpath option at configuration time. This option will instruct the linker to always look for the libraries where they are installed. You will need to use the appropriate linker options when linking your own applications and libraries against ICU, too. Please refer to your system's linker manual for information about runtime paths. The use of rpath also means that when building a new version of ICU you should not have an older version installed in the same place as the new version's installation directory, as the older libraries will used during the build, instead of the new ones, likely leading to an incorrectly build ICU. This is the proper behavior of rpath.
If you are using ICU's Makefiles to build ICU on a new platform, there are a few places where you will need to add or modify some files. If you need more help, you can always ask the icu-support mailing list. Once you have finished porting ICU to a new platform, it is recommended that you contribute your changes back to ICU via the icu-support mailing list. This will make it easier for everyone to benefit from your work.
For some people, it may not be necessary for completely build ICU. Most of the makefiles and build targets are for tools that are used for building ICU's data, and an application's data (when an application uses ICU resource bundles for its data).
Data files can be built on a different platform when both platforms share the same endianness and the same charset family. This assertion does not include platform dependent DLLs/shared/static libraries. For details see the User Guide ICU Data chapter.
ICU 3.6 removes the requirement that ICU be completely built in the native operating environment. It adds the icupkg tool which can be run on any platform to turn binary ICU data files from any one of the three formats into any one of the other data formats. This allows a application to use ICU data built anywhere to be used for any other target platform.
WARNING! Building ICU without running the tests is not recommended. The tests verify that ICU is safe to use. It is recommended that you try to completely port and test ICU before using the libraries for your own application.
Try to follow the build steps from the UNIX
build instructions. If the configure script fails, then you will need to
modify some files. Here are the usual steps for porting to a new
platform:
The platform dependencies have been mostly isolated into the following files in the common library. This information can be useful if you are porting ICU to a new platform.
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