如何解决Debian下编译Qt/C++代码时的Position Independent Code错误

Hey there, let's sort out that PIC error you're facing when running make on the MECAGEN Qt/C++ project. This is a common issue on Debian (and other Debian-based distros) where GCC enforces position-independent code requirements for certain build targets, especially shared libraries. Here's how to fix it step by step:

1. Add -fPIC to Your Compilation Flags #

First, check the project's Makefile for compiler flags. The -fPIC flag tells GCC to generate position-independent code, which is required for linking into shared libraries.

• Open the project's Makefile in a text editor. Look for lines starting with CXXFLAGS (for C++) or CFLAGS (for C).
• If -fPIC isn't already present, add it to the flags. For example:

  # Before
  CXXFLAGS += -Wall -O2
  # After
  CXXFLAGS += -Wall -O2 -fPIC
  

• If the Makefile was generated by Qt's qmake (look for a .pro file in the project), edit the .pro file instead and add:

  QMAKE_CXXFLAGS += -fPIC
  

  Then re-run qmake to regenerate the Makefile before running make.

2. Clean Old Build Files and Recompile #

Cached object files from previous builds might still use the old flags. Clear them first to ensure the new settings take effect:

make clean
make

3. Handle Static Libraries Linked to Shared Libraries #

If the project includes static libraries that get linked into a shared library, those static libraries also need to be compiled with -fPIC. Check for any static library targets in the Makefile and add -fPIC to their compilation flags too.

4. Test with Explicit Flag Override #

If you want to quickly verify that -fPIC is the fix without editing files, you can override the flags directly in the make command:

make CXXFLAGS="-fPIC -Wall -O2"

This forces the compiler to use the PIC flag for that single build run, which helps confirm if it resolves the error.

内容的提问来源于stack exchange，提问作者Joel