eteran / gdtoa-desktop

Binary-decimal floating-point conversion library by David M. Gay

gdtoa-desktop

This is an adaptation of the binary↔decimal floating-point conversion library by David M. Gay to common desktop/server operating systems like Ubuntu and Fedora.

This adapatation's main objective is to provide an easy way to build the original upstream library in the configuration well-suited for the target systems – with locale and multithreading support, and without conflicts with the system libraries like glibc.

How it compares to the original library

The original library is contained verbatim in the gdtoa directory in the root of the source tree. All the adaptations are made using CMakeLists.txt and source files outside that directory.

Unlike the makefile of the original library, CMake-based build system here enables some options and applies some tweaks:

• USE_LOCALE, since any glibc-based apps looking for a compatible parsing and formatting of numbers will need it
• MULTIPLE_THREADS + the required locking functions, since the target OSes are multithreaded, and we intend this library to be usable generically.
• All the externally-visible function names have been prefixed by gdtoa_ prefix. So, if you wanted to call e.g. g_xfmt(args...), you should instead use gdtoa_g_xfmt(args...).
• For 32-bit x86 systems SSE2 is used for arithmetic instead of x87 to avoid inconsistent rounding. Then strtodt test passes. If you target a CPU without SSE2 support, set the GDTOA_ENABLE_SSE2 option to OFF. In this case the implementation using integer arithmetic will be compiled into the library.

Installation

Simply doing the following commands should be enough to install the library:

mkdir build
cd build
cmake ..
make
make install

This will install the following files:

/usr/local/lib/libgdtoa-desktop.so
/usr/local/lib/pkgconfig/gdtoa-desktop.pc
/usr/local/include/gdtoa-desktop/arith.h
/usr/local/include/gdtoa-desktop/gdtoa-desktop.h

Running tests

After configuring the package using the cmake command, run

make check

This will run tests from the original library.

Manually upgrading to a newer upstream version

Generally, it's suggested to try doing git pull to see if this repo is already up to date. But if this repo lags behind while you need to use a newer upstream version of the library retaining the tweaks made here, you can upgrade your local copy manually like follows:

1. Remove old gdtoa/ directory.
2. Extract the new one in its place.
3. Build (but don't install) the library, passing -DGDTOA_RENAME_FUNCTIONS=OFF parameter to cmake.
4. Use the resulting library libgdtoa-desktop.so to generate the list of externally-visible functions. You can find the commands for generation in the comments in rename-functions.sh and CMakeLists.txt (grep for '<nm>' there).
5. Having generated the two lists, update them in the corresponding places in these two files.
6. If any new *.c files appeared in the original library, add them to gdtoa_SOURCES in the CMakeLists.txt

Now you should be able to simply build the upgraded library as usual, not forgetting to reset GDTOA_RENAME_FUNCTIONS option back to ON.

NOTE: this procedure totally ignores tests, which may need tweaking of CMakeLists.txt and run-tests.sh after upgrade.