Using command-line options to control the generation of C++ exception tables

By default, or if the option --exceptions is specified, the image can contain exception tables. Exception tables are discarded silently if no code throws an exception. However, if the option --no_exceptions is specified, the linker generates an error if any exceptions sections are present after unused sections have been eliminated.

You can use the --no_exceptions option to ensure that your code is exceptions free. The linker generates an error message to highlight that exceptions have been found and does not produce a final image.

However, you can use the --no_exceptions option with the --diag_warning option to downgrade the error message to a warning. The linker produces a final image but also generates a message to warn you that exceptions have been found.

The linker can create exception tables for legacy objects that contain debug frame information. The linker can do this safely for C and assembly language objects. By default, the linker does not create exception tables. This is the same as using the linker option --exceptions_tables=nocreate.

The linker option --exceptions_tables=unwind enables the linker to use the .debug_frame information to create a register-restoring unwinding table for each section in your image that does not already have an exception table. If this is not possible, the linker creates a nounwind table instead.

Use the linker option --exceptions_tables=cantunwind to create a nounwind table for each section in your image that does not already have an exception table.


Be aware of the following:

  • With the default settings, that is, --exceptions --exceptions_tables=nocreate, it is not safe to throw an exception through C or assembly code, unless the C code is compiled with the option --exceptions.

  • The linker can generate frame unwinding instructions from objects with .debug_frame information. Frame unwinding is sufficient for C and assembler code. It is not sufficient for C++ code, because it does not call the destructors for the objects on the stack that is being unwound.

    The cleanup code for C++ must be generated by the compiler with the --exceptions option.

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