How to Resolve Static Linking Errors When Connecting to an Oracle Database in CGO on Linux/Ubuntu?

Troubleshooting Static Linking of Oracle Libraries in CGO Executables on Linux/Ubuntu

You're attempting to build a static binary that connects to an Oracle database but encounter an error during the linking phase. Here's a detailed analysis and solution to your problem:

Linking Error

/usr/bin/ld: cannot find -lclntsh

This error indicates that the compiler cannot locate the Oracle library libclntsh.a.

Investigation

Your configuration already includes the dynamic version of the library (-L/usr/lib/oracle/12.1/client64/lib -lclntsh) for dynamic linking, but you need to use the static version (.a) for static linking.

Solution

To build a static CGO executable with Oracle libraries, you must follow these steps:

1. Use Oracle's relink Tool: Use the $ORACLE_HOME/bin/relink tool to generate the static library named libclntst.a:

   $ORACLE_HOME/bin/relink all

2. Link Your App with libclntst.a: Try linking your application with the static library:

   CGO_ENABLED=1  go build -work -x -ldflags  " -v -linkmode external -extldflags -static" -L/usr/lib/oracle/12.1/client64/lib  oracletest.go

3. Identify Missing Symbols: If you encounter additional errors, use the nm tool to find the source of those missing symbols.
4. Link with Missing Libraries: Link with the libraries that provide the missing symbols. In most cases, you will need to link with additional Oracle libraries or statically compiled versions of any other C libraries that your Oracle libraries depend on.

Example

For example, the following command successfully builds a statically linked executable on 11gR2:

/usr/bin/c++ -Wall -ggdb3 -fPIC \
 CMakeFiles/opassgen.dir/opassgen.cpp.o \
 CMakeFiles/opassgen.dir/dbutils.cpp.o \
 CMakeFiles/opassgen.dir/common.cpp.o  \
 CMakeFiles/opassgen.dir/crypto.cpp.o  \
 n.o  -o opassgen                      \
 -rdynamic -static-libgcc -L. -Wl,-Bstatic -lstdc++ -Wl,-Bdynamic \
 /home/oracle/ivan/openssl-1.0.1t/libcrypto.a  \
 /oracle/u01/db/11.2.0.4/lib/libclntst11.a     \
 /oracle/u01/db/11.2.0.4/lib/libippdcmerged.a  \
 /oracle/u01/db/11.2.0.4/lib/libippsmerged.a   \
 -Wl,--whole-archive libtrotl.a -Wl,--no-whole-archive \
 -lpthread -ldl

Conclusion

Building statically linked CGO executables with Oracle libraries can be challenging due to multiple library dependencies. By following the solutions provided, you can successfully generate a static binary that connects to your Oracle database.

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