Gcc compilation "cannot compute suffix of object files: cannot compile"

Resolving 'cannot compute suffix of object files' in GCC Compilation

Understand and troubleshoot the 'cannot compute suffix of object files: cannot compile' error encountered during GCC compilation, especially in Linux From Scratch environments.

When compiling software, particularly in a meticulously controlled environment like Linux From Scratch (LFS), encountering cryptic error messages can be a significant hurdle. One such error is cannot compute suffix of object files: cannot compile. This message indicates a fundamental problem with the GCC compiler's ability to process source files into object files, often pointing to issues with the compiler's configuration, environment, or the underlying system's C library.

Understanding the Error

The error cannot compute suffix of object files: cannot compile typically arises when GCC attempts to determine the file extension for intermediate object files (e.g., .o for C, .obj for Windows) but fails. This failure isn't usually due to a simple typo in a filename. Instead, it often signifies that the compiler itself cannot successfully execute its core function: compiling a basic source file. This can happen for several reasons, including:

1. Missing or Corrupt C Library (glibc): GCC relies heavily on the C standard library (glibc) for fundamental operations. If glibc is missing, incorrectly installed, or corrupted, GCC might fail to compile even the simplest test programs.
2. Incorrect Compiler Configuration: During the configure stage of GCC, paths to libraries, headers, and other essential components are determined. If these paths are wrong or point to non-existent resources, the compiler will be unable to function correctly.
3. Environment Variable Issues: Environment variables like PATH, LD_LIBRARY_PATH, or CPATH can influence how GCC locates its dependencies. Incorrect settings can lead to the compiler not finding necessary tools or libraries.
4. Cross-Compilation Setup Problems: In cross-compilation scenarios (e.g., building for a different architecture), misconfigurations in the target triplet or sysroot can cause this error.

flowchart TD
    A[Start Compilation] --> B{GCC attempts to compile a test file}
    B --> C{GCC determines object file suffix}
    C -- Fails --> D["Error: cannot compute suffix of object files: cannot compile"]
    D --> E{Root Cause Analysis}
    E -- Missing/Corrupt glibc --> F[Rebuild/Verify glibc]
    E -- Incorrect GCC Config --> G[Re-configure/Rebuild GCC]
    E -- Environment Variable Issue --> H[Check/Set Environment Variables]
    E -- Cross-Comp. Setup --> I[Verify Target/Sysroot]
    C -- Succeeds --> J[Continue Compilation]
    F --> B
    G --> B
    H --> B
    I --> B

Flowchart of GCC Compilation Failure and Troubleshooting Steps

Common Scenarios and Solutions

This error is particularly prevalent in LFS builds where the system is built from scratch, and every component's dependency and path must be precisely managed. Here's how to approach troubleshooting:

1. Verify glibc Installation

The most common culprit in LFS is an issue with glibc. GCC needs a functional C library to compile even the most basic C programs. If glibc was not built correctly or is missing, GCC will fail. You can often test this by trying to compile a very simple C program manually.

Solution: Ensure glibc is correctly installed and accessible. In an LFS context, this often means re-checking the glibc build steps, especially the configure and make install phases. Verify that the necessary libc.so and header files are in their expected locations (e.g., /lib, /usr/lib, /usr/include).

2. Check GCC Configuration and Build

The configure script for GCC sets up all the paths and dependencies. If it was run with incorrect options or couldn't find necessary components, the resulting compiler might be broken.

Solution: Review the configure command used for GCC. Ensure that --with-glibc-version, --with-sysroot, and other critical paths are correctly specified. If in doubt, clean the GCC build directory and re-run the configure and make steps carefully, following the LFS book's instructions precisely.

3. Environment Variables

Incorrect PATH or LD_LIBRARY_PATH can prevent GCC from finding its own components or the C library.

Solution: Check your shell's environment variables. Ensure that /usr/bin (where GCC usually resides) and the paths to your C library are correctly included in PATH and LD_LIBRARY_PATH respectively. For LFS, it's crucial to be in the chroot environment with the correct environment variables sourced.

4. Simple Test Compilation

Try to compile a minimal C program to isolate the issue. If this fails, the problem is with the compiler setup itself.

Solution: Create a file named test.c with the following content:

#include <stdio.h>

int main() {
    printf("Hello, GCC!\n");
    return 0;
}

A minimal C program to test GCC functionality.

Then, try to compile it:

gcc test.c -o test

Attempting to compile the test program.

If this command fails with the cannot compute suffix error, it confirms a core compiler issue. If it produces a different error, that new error message will provide more specific clues.

Advanced Troubleshooting for LFS

In an LFS context, the error often means that the temporary toolchain (Chapter 5) or the final toolchain (Chapter 6) was not built correctly, or that the system is trying to use a mix of host and LFS tools/libraries.

1. Check ldd Output: For any executable (like gcc itself), ldd can show which shared libraries it's linked against. If ldd $(which gcc) shows missing libraries or libraries from the host system (outside the LFS chroot), you have a pathing or library issue.
2. Re-read LFS Instructions: The LFS book is highly precise. A single missed step or incorrect command can lead to cascading failures. Pay close attention to chroot entries, environment variable settings, and configure flags.
3. Temporary Toolchain Integrity: The temporary toolchain built in Chapter 5 is critical. If it's flawed, subsequent builds (including the final GCC) will also be flawed. If you suspect issues, it might be necessary to revert to an earlier snapshot or restart Chapter 5.

1. Verify glibc presence

Check if libc.so.6 exists in /lib or /usr/lib within your LFS chroot. If not, glibc is likely missing or incorrectly installed.

2. Test basic compilation

Create a simple test.c file and attempt to compile it with gcc test.c -o test. Observe the exact error message.

3. Inspect environment variables

Run env inside your chroot and verify that PATH, LD_LIBRARY_PATH, and other relevant variables are set according to the LFS book's instructions.

4. Review GCC build logs

Examine the config.log and make.log files from your GCC build directory for earlier errors that might have been overlooked.

5. Consider re-building GCC/glibc

If all else fails, a clean rebuild of glibc and then gcc (or even the entire Chapter 5 toolchain) might be necessary, paying extreme attention to every instruction.