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:
-data-evaluate-expression --language c "sizeof (void*)"
^done,value="4"
gdb/ChangeLog:
* mi/mi-parse.h (struct mi_parse) <language>: New field.
* 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.
* NEWS: Add entry mentioning the new "--language" command option.
gdb/testsuite/ChangeLog:
* gdb.mi/mi-language.exp: New file.
gdb/doc/ChangeLog:
* gdb.texinfo (Show): Add xref anchor for "show language" command.
(Context management): Place current subsection text into its own
subsubsection. Add new subsubsection describing the "--language"
command option.
