Diagnosis and Resolution of C Compiler Executable Creation Failure on macOS Lion

Problem Background and Error Analysis

When installing memcached on macOS Lion operating systems, developers frequently encounter a typical compilation configuration error: configure: error: C compiler cannot create executables. This error occurs during the software package configuration phase using the GNU Autoconf toolchain, indicating that while the C compiler is detected, it cannot successfully compile and generate executable files.

Root Cause Diagnosis

By analyzing the provided config.log file, we can identify several critical issues:

First, the compiler version information shows: i686-apple-darwin9-gcc-4.0.1 (GCC) 4.0.1 (Apple Inc. build 5484). This GCC 4.0.1 version is clearly outdated, likely remnants of development tools migrated from older macOS versions.

Second, the error message during the linking phase: ld: library not found for -lcrt1.10.5.o indicates that the linker cannot find necessary C runtime library files. This error further confirms the incompleteness of the development toolchain.

Core Solution: Updating Xcode Command Line Tools

For macOS Lion systems, the most effective solution is to install or update Xcode Command Line Tools:

1. First ensure the latest version of Xcode is installed. For Lion systems, Xcode 4.3 or later is recommended.

2. Launch the Xcode application and navigate to the Preferences settings panel.

3. Select the Locations tab and choose the appropriate tool version from the Command Line Tools dropdown menu.

4. If no options are available in the dropdown menu, click the Install button to download and install the Command Line Tools package.

Environment Verification and Testing

After installation, verify that the development environment is properly configured:

gcc --version

The correct output should display a newer GCC version (such as 4.2.1 or later), rather than the previously seen 4.0.1 version.

To test compiler functionality completeness, create a simple test program:

echo "int main() { return 0; }" > test.c
gcc test.c -o test
./test
echo $?

If the return value is 0, it confirms the compiler can now normally create executable files.

Supplementary Solution References

Beyond the primary Command Line Tools update solution, other potential resolution methods include:

1. Xcode License Agreement Acceptance: In some cases, even with correct tools installed, accepting Xcode's license agreement is necessary:

sudo xcodebuild -license

Follow the prompts to read and accept the license terms.

2. Toolchain Path Repair: If specific toolchain path issues are encountered, create symbolic links:

cd /Applications/Xcode.app/Contents/Developer/Toolchains
sudo ln -s XcodeDefault.xctoolchain OSX10.7.xctoolchain

Preventive Measures and Best Practices

To prevent recurrence of similar issues, developers are advised to:

1. Promptly update all development tools after system upgrades

2. Regularly check development environment configuration status

3. Use package managers like Homebrew or MacPorts to manage open-source software dependencies

4. Maintain version synchronization between Xcode and Command Line Tools

Conclusion

The C compiler cannot create executables error in macOS Lion systems typically stems from outdated or incomplete development toolchain configurations. By updating Xcode Command Line Tools and ensuring proper environment variable settings, developers can quickly restore normal compilation environments. Understanding diagnostic information from config.log files is crucial for rapidly identifying and resolving such issues.