第 3 章 Debugging Applications

Procedure

1. Compile and link your code with the -g option to generate debugging information:

   $ gcc ... -g ...

2. Optional: Set the optimization level to -Og:

   $ gcc ... -g -Og ...

   Compiler optimizations can make executable code hard to relate to the source code. The -Og option optimizes the code without interfering with debugging. However, be aware that changing optimization levels can alter the program’s behavior.

3. Optional: Use -g for moderate debugging information, or -g3 to include macro definitions:

   $ gcc ... -g3 ...

Procedure

1. Start GDB attached to the application or library you want to debug. GDB automatically recognizes missing debugging information and suggests a command to run.

   $ gdb -q /bin/ls

   Reading symbols from /bin/ls...Reading symbols from .gnu_debugdata for /usr/bin/ls...(no debugging symbols found)...done.
   (no debugging symbols found)...done.
   Missing separate debuginfos, use: dnf debuginfo-install coreutils-9.5-6.el10.x86_64
   (gdb)

2. Exit GDB: type q and confirm with Enter.

   (gdb) q

3. Run the command suggested by GDB to install the required debuginfo packages:

   # dnf debuginfo-install coreutils-9.5-6.el10.x86_64

   The dnf package management tool provides a summary of the changes, asks for confirmation and once you confirm, downloads and installs all the necessary files.

4. In case GDB is not able to suggest the debuginfo package, follow the procedure described in

   • Getting debuginfo packages for an application or library manually.

Procedure

1. Find the executable file of the application or library.

   1. Use the which command to find the application file.

      $ which less

      /usr/bin/less

   2. Use the locate command to find the library file.

      $ locate libz | grep so

      /usr/lib64/libz.so.1
      /usr/lib64/libz.so.1.2.11

      If your debugging started from error messages, choose the path where the library file name includes the same numbers as the messages. If you are unsure, continue with the path where the file name has no extra numbers.

2. Search for a name and version of the package that provided the file:

   $ rpm -qf /usr/lib64/libz.so.1.3.1.zlib-ng

   zlib-ng-compat-2.2.3-1.el10.x86_64

   The output provides details for the installed package in the name:epoch-version.release.architecture format.

   重要

   If this step does not produce any results, it is not possible to determine which package provided the binary file. There are several possible cases:

   • The file is installed from a package which is not known to package management tools in their current configuration.
   • The file is installed from a locally downloaded and manually installed package. Determining a suitable debuginfo package automatically is impossible in that case.
   • Your package management tools are misconfigured.
   • The file is not installed from any package. In such a case, no corresponding debuginfo package exists.

   Because further steps depend on this one, you must resolve this situation or stop this procedure. Describing the exact troubleshooting steps is beyond the scope of this procedure.

3. Install the debuginfo packages using the dnf debuginfo-install utility. In the command, use the package name and other details you determined during the previous step:

   # dnf debuginfo-install zlib-ng-compat-2.2.3-1.el10.x86_64