Building C API Client Programs

This section provides guidelines for compiling C programs that use the MySQL C API.

Compiling MySQL Clients on Unix

You may need to specify an -I option when you compile client programs that use MySQL header files, so that the compiler can find them. For example, if the header files are installed in /usr/local/mysql/include, use this option in the compile command:


MySQL clients must be linked using the -lmysqlclient -lz options in the link command. You may also need to specify a -L option to tell the linker where to find the library. For example, if the library is installed in /usr/local/mysql/lib, use these options in the link command:

-L/usr/local/mysql/lib -lmysqlclient -lz

The path names may differ on your system. Adjust the -I and -L options as necessary.

To make it simpler to compile MySQL programs on Unix, use the mysql_config script. See Section 4.7.2, “mysql_config — Display Options for Compiling Clients”.

mysql_config displays the options needed for compiling or linking:

shell> mysql_config --cflags
shell> mysql_config --libs

You can run those commands to get the proper options and add them manually to compilation or link commands. Alternatively, include the output from mysql_config directly within command lines using backticks:

shell> gcc -c `mysql_config --cflags` progname.c
shell> gcc -o progname progname.o `mysql_config --libs`
Compiling MySQL Clients on Microsoft Windows

To specify header and library file locations, use the facilities provided by your development environment.

On Windows, you can link your code with either the dynamic or static C client library. The static library is named mysqlclient.lib and the dynamic library is named libmysql.dll. In addition, the libmysql.lib static import library is needed for using the dynamic library.

If you link with the static library, failure can occur unless these conditions are satisfied:

  • The client application must be compiled with the same version of Visual Studio used to compile the library.

  • The client application should link the C runtime statically by using the /MT compiler option.

If the client application is built in in debug mode and uses the static debug C runtime (/MTd compiler option), it can link to the mysqlclient.lib static library if that library was built using the same option. If the client application uses the dynamic C runtime (/MD option, or /MDd option in debug mode), it must must be linked to the libmysql.dll dynamic library. It cannot link to the static client library.

The MSDN page describing the link options can be found here: http://msdn.microsoft.com/en-us/library/2kzt1wy3.aspx

Troubleshooting Problems Linking to the MySQL Client Library

Linking with the single-threaded library (libmysqlclient) may lead to linker errors related to pthread symbols. When using the single-threaded library, please compile your client with MYSQL_CLIENT_NO_THREADS defined. This can be done on the command line by using the -D option to the compiler, or in your source code before including the MySQL header files. This define should not be used when building for use with the thread-safe client library (libmysqlclient_r).

If the linker cannot find the MySQL client library, you might get undefined-reference errors for symbols that start with mysql_, such as those shown here:

/tmp/ccFKsdPa.o: In function `main':
/tmp/ccFKsdPa.o(.text+0xb): undefined reference to `mysql_init'
/tmp/ccFKsdPa.o(.text+0x31): undefined reference to `mysql_real_connect'
/tmp/ccFKsdPa.o(.text+0x69): undefined reference to `mysql_error'
/tmp/ccFKsdPa.o(.text+0x9a): undefined reference to `mysql_close'

You should be able to solve this problem by adding -Ldir_path -lmysqlclient at the end of your link command, where dir_path represents the path name of the directory where the client library is located. To determine the correct directory, try this command:

shell> mysql_config --libs

The output from mysql_config might indicate other libraries that should be specified on the link command as well. You can include mysql_config output directly in your compile or link command using backticks. For example:

shell> gcc -o progname progname.o `mysql_config --libs`

If an error occurs at link time that the floor symbol is undefined, link to the math library by adding -lm to the end of the compile/link line.

If you get undefined reference errors for the uncompress or compress function, add -lz to the end of your link command and try again.

Similarly, if you get undefined-reference errors for other functions that should exist on your system, such as connect(), check the manual page for the function in question to determine which libraries you should add to the link command.

If you get undefined-reference errors such as the following for functions that do not exist on your system, it usually means that your MySQL client library was compiled on a system that is not 100% compatible with yours:

mf_format.o(.text+0x201): undefined reference to `__lxstat'

In this case, you should download the latest MySQL or Connector/C source distribution and compile the MySQL client library yourself. See Section 2.17, “Installing MySQL from Source”, and MySQL Connector/C Developer Guide.

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