Re: [RFC 3/3] GDB/MI: Add new "--language LANG" command option.

[Pedro Alves <palves at redhat dot com>]

On 11/11/2013 06:37 AM, Joel Brobecker wrote:
> Hello,
> 
> Frontend sometimes need to evaluate expressions that are
> language-specific. For instance, Eclipse uses the following
> expression to determine the size of an address on the target:
> 
>     -data-evaluate-expression "sizeof (void*)"
> 
> Unfortunately, if the main of the program being debugged is not C,
> this may not work. For instance, if the main is in Ada, you get...
> 
>     -data-evaluate-expression "sizeof (void*)"
>     ^error,msg="No definition of \"sizeof\" in current context."
> 
> ... and apparently decides to stop the debugging session as a result.
> The  recommendation sent was to specifically set the language to C
> before trying to evaluate the expression.  Something such as:
> 
>     1. save current language
>     2. set language c
>     3. -data-evaluate-expression "sizeof (void*)"
>     4. Restore language
> 
> This has the same disadvantages as the ones outlined in the "Context
> Management" section of the GDB/MI documentation regarding setting
> the current thread or the current frame, thus recommending the use of
> general command-line switches such as --frame, or --thread instead.
> 
> This patch follows the same steps for the language, adding a similar
> new command option: --language LANG. Example of use:

Makes sense to me.  I skimmed the patch and it looked fine.

> 
>     -data-evaluate-expression --language c "sizeof (void*)"
>     ^done,value="4"
> 
> gdb/ChangeLog:
> 
>         * mi/mi-parse.h (struct mi_parse) [language]: New field.

[] is used for conditionally compiled code (#if FOO).  For specifying
context, use <>.

>         * mi/mi-main.c (mi_cmd_execute): Temporarily set language to
>         PARSE->LANGUAGE during command execution, if set.
>         * mi/mi-parse.c: Add "language.h" #include.
>         (mi_parse): Add parsing of "--language" command option.

-- 
Pedro Alves