Resolving the undefined stat Symbol Error When Compiling with -fPIC

Learn how to troubleshoot and solve the `undefined stat` symbol error encountered during the compilation of static libraries with `-fPIC`. Discover the steps to ensure proper compilation and linking.
---

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: undefined stat symbol after compiling with -fPIC

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
How to Solve the undefined stat Symbol Error After Compiling with -fPIC

If you've ever encountered the dreaded undefined symbol stat error while working with external static libraries in C or C++, you know just how frustrating it can be. This issue can arise when compiling your program with the -fPIC (Position Independent Code) flag, especially when using libraries like zmq.a. In this guide, we will dissect the problem, understand why it happens, and explore a solution that can save you time and headaches.

Understanding the Problem

During the compilation of your program, the following message may pop up if you use an external static library:

[[See Video to Reveal this Text or Code Snippet]]

This warning indicates that the library zmq.a wasn't compiled with the -fPIC flag. If you attempt to ignore the warning and proceed to compile your application, you may successfully compile it but run into a runtime error—specifically, the "undefined symbol stat" error. This occurs when the linker cannot find the implementation for the stat function that your program expects to use.

The Core of the Issue

The root of the problem lies in the overriding of compiler flags. When you compile a library and set various flags (like CFLAGS and CXXFLAGS), if you mistakenly override critical flags needed for linkage (like optimization flags), you may inadvertently cause linker errors. In this case, the flag -O2, which optimizes the code, was overridden, leading to the missing symbol.

Breaking Down the Solution

To resolve the undefined symbol stat error alongside ensuring that your library can be compiled with the -fPIC flag, follow these organized steps:

Step 1: Recompile the Library Correctly

You need to ensure that the library is compiled properly with the -fPIC flag without unintentionally overriding other necessary flags. Here’s how to do that:

Navigate to your library's source directory in the terminal.

Execute the following command sequence to compile the library, ensuring -fPIC is included without overriding other flags:

[[See Video to Reveal this Text or Code Snippet]]

Steps Explained

autoreconf --install: This prepares the build system by generating the necessary configuration files.

mkdir build: Creates a new directory for the build files.

cd build: Moves into the build directory.

../configure: Configures the build settings based on your system and desired options.

make: Compiles the library using specified flags, ensuring both position independence and optimization.

make install: Installs the compiled library onto your system.

Step 2: Compile Your Main Application

With the library now properly compiled, you can compile your own application without any issues. Make sure to include the appropriate flags as necessary, for example:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

Debugging the undefined symbol stat issue can be challenging, but by ensuring that the external library is compiled with the correct flags without overshadowing others, you can effectively sidestep this common pitfall. If you follow the steps laid out in this guide, you should be able to compile both zmq.a and your application seamlessly. Happy coding!