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Don't throw Scheme exceptions with live std::vector objects

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A complication with the Guile code is that we have two types of
exceptions to consider: GDB/C++ exceptions, and Guile/SJLJ exceptions.

Because Guile exceptions are SJLJ based, we must make sure to not have
live local variables of types with non-trivial dtors when a Guile
exception is thrown, because the dtors won't be run when a Guile
exceptions is thrown.

gdbscm_parse_function_args currently violates this:

 void
 gdbscm_parse_function_args (const char *func_name,
			     int beginning_arg_pos,
			     const SCM *keywords,
			     const char *format, ...)
 {
 ...
   /* Keep track of malloc'd strings.  We need to free them upon error.  */
   std::vector<char *> allocated_strings;
 ...
   for (char *ptr : allocated_strings)
     xfree (ptr);
   gdbscm_throw (status); /// dtor of "allocated_strings" is not run!
 }

This commit fixes the above making using of gdbscm_wrap.

It would be nice if we had a way to make it impossible to write such
code.  PR guile/23429 has an idea for that, if someone's interested.

gdb/ChangeLog:
2018-08-21  Pedro Alves  <palves@redhat.com>

	* guile/scm-utils.c (gdbscm_parse_function_args_1): New, factored
	out from gdbscm_parse_function_args.
	(gdbscm_parse_function_args): Rework to use gdbscm_wrap and
	gdbscm_parse_function_args_1.
This commit is contained in:
Pedro Alves 2018-08-21 16:48:30 +01:00
parent ae19acf320
commit 4895f384b4
2 changed files with 105 additions and 77 deletions
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7
gdb/ChangeLog
View File

@ -1,3 +1,10 @@
2018-08-21 Pedro Alves <palves@redhat.com>
* guile/scm-utils.c (gdbscm_parse_function_args_1): New, factored
out from gdbscm_parse_function_args.
(gdbscm_parse_function_args): Rework to use gdbscm_wrap and
gdbscm_parse_function_args_1.
2018-08-21 Simon Marchi <simon.marchi@ericsson.com>
PR gdb/17816

175
gdb/guile/scm-utils.c
View File

@ -306,80 +306,18 @@ lookup_keyword (const SCM *keyword_list, SCM keyword)
return -1;
}
/* Utility to parse required, optional, and keyword arguments to Scheme
functions. Modelled on PyArg_ParseTupleAndKeywords, but no attempt is made
at similarity or functionality.
There is no result, if there's an error a Scheme exception is thrown.
Guile provides scm_c_bind_keyword_arguments, and feel free to use it.
This is for times when we want a bit more parsing.
/* Helper for gdbscm_parse_function_args that does most of the work,
in a separate function wrapped with gdbscm_wrap so that we can use
non-trivial-dtor objects here. The result is #f upon success or a
<gdb:exception> object otherwise. */
BEGINNING_ARG_POS is the position of the first argument passed to this
routine. It should be one of the SCM_ARGn values. It could be > SCM_ARG1
if the caller chooses not to parse one or more required arguments.
KEYWORDS may be NULL if there are no keywords.
FORMAT:
s - string -> char *, malloc'd
t - boolean (gdb uses "t", for biT?) -> int
i - int
u - unsigned int
l - long
n - unsigned long
L - longest
U - unsigned longest
O - random scheme object
| - indicates the next set is for optional arguments
# - indicates the next set is for keyword arguments (must follow |)
. - indicates "rest" arguments are present, this character must appear last
FORMAT must match the definition from scm_c_{make,define}_gsubr.
Required and optional arguments appear in order in the format string.
Afterwards, keyword-based arguments are processed. There must be as many
remaining characters in the format string as their are keywords.
Except for "|#.", the number of characters in the format string must match
#required + #optional + #keywords.
The function is required to be defined in a compatible manner:
#required-args and #optional-arguments must match, and rest-arguments
must be specified if keyword args are desired, and/or regular "rest" args.
Example: For this function,
scm_c_define_gsubr ("execute", 2, 3, 1, foo);
the format string + keyword list could be any of:
1) "ss|ttt#tt", { "key1", "key2", NULL }
2) "ss|ttt.", { NULL }
3) "ss|ttt#t.", { "key1", NULL }
For required and optional args pass the SCM of the argument, and a
pointer to the value to hold the parsed result (type depends on format
char). After that pass the SCM containing the "rest" arguments followed
by pointers to values to hold parsed keyword arguments, and if specified
a pointer to hold the remaining contents of "rest".
For keyword arguments pass two pointers: the first is a pointer to an int
that will contain the position of the argument in the arg list, and the
second will contain result of processing the argument. The int pointed
to by the first value should be initialized to -1. It can then be used
to tell whether the keyword was present.
If both keyword and rest arguments are present, the caller must pass a
pointer to contain the new value of rest (after keyword args have been
removed).
There's currently no way, that I know of, to specify default values for
optional arguments in C-provided functions. At the moment they're a
work-in-progress. The caller should test SCM_UNBNDP for each optional
argument. Unbound optional arguments are ignored. */
void
gdbscm_parse_function_args (const char *func_name,
int beginning_arg_pos,
const SCM *keywords,
const char *format, ...)
static SCM
gdbscm_parse_function_args_1 (const char *func_name,
int beginning_arg_pos,
const SCM *keywords,
const char *format, va_list args)
{
va_list args;
const char *p;
int i, have_rest, num_keywords, position;
int have_optional = 0;
@ -391,8 +329,6 @@ gdbscm_parse_function_args (const char *func_name,
have_rest = validate_arg_format (format);
num_keywords = count_keywords (keywords);
va_start (args, format);
p = format;
position = beginning_arg_pos;
@ -511,15 +447,100 @@ gdbscm_parse_function_args (const char *func_name,
}
}
va_end (args);
return;
/* Return anything not-an-exception. */
return SCM_BOOL_F;
fail:
va_end (args);
for (char *ptr : allocated_strings)
xfree (ptr);
gdbscm_throw (status);
/* Return the exception, which gdbscm_wrap takes care of
throwing. */
return status;
}
/* Utility to parse required, optional, and keyword arguments to Scheme
functions. Modelled on PyArg_ParseTupleAndKeywords, but no attempt is made
at similarity or functionality.
There is no result, if there's an error a Scheme exception is thrown.
Guile provides scm_c_bind_keyword_arguments, and feel free to use it.
This is for times when we want a bit more parsing.
BEGINNING_ARG_POS is the position of the first argument passed to this
routine. It should be one of the SCM_ARGn values. It could be > SCM_ARG1
if the caller chooses not to parse one or more required arguments.
KEYWORDS may be NULL if there are no keywords.
FORMAT:
s - string -> char *, malloc'd
t - boolean (gdb uses "t", for biT?) -> int
i - int
u - unsigned int
l - long
n - unsigned long
L - longest
U - unsigned longest
O - random scheme object
| - indicates the next set is for optional arguments
# - indicates the next set is for keyword arguments (must follow |)
. - indicates "rest" arguments are present, this character must appear last
FORMAT must match the definition from scm_c_{make,define}_gsubr.
Required and optional arguments appear in order in the format string.
Afterwards, keyword-based arguments are processed. There must be as many
remaining characters in the format string as their are keywords.
Except for "|#.", the number of characters in the format string must match
#required + #optional + #keywords.
The function is required to be defined in a compatible manner:
#required-args and #optional-arguments must match, and rest-arguments
must be specified if keyword args are desired, and/or regular "rest" args.
Example: For this function,
scm_c_define_gsubr ("execute", 2, 3, 1, foo);
the format string + keyword list could be any of:
1) "ss|ttt#tt", { "key1", "key2", NULL }
2) "ss|ttt.", { NULL }
3) "ss|ttt#t.", { "key1", NULL }
For required and optional args pass the SCM of the argument, and a
pointer to the value to hold the parsed result (type depends on format
char). After that pass the SCM containing the "rest" arguments followed
by pointers to values to hold parsed keyword arguments, and if specified
a pointer to hold the remaining contents of "rest".
For keyword arguments pass two pointers: the first is a pointer to an int
that will contain the position of the argument in the arg list, and the
second will contain result of processing the argument. The int pointed
to by the first value should be initialized to -1. It can then be used
to tell whether the keyword was present.
If both keyword and rest arguments are present, the caller must pass a
pointer to contain the new value of rest (after keyword args have been
removed).
There's currently no way, that I know of, to specify default values for
optional arguments in C-provided functions. At the moment they're a
work-in-progress. The caller should test SCM_UNBNDP for each optional
argument. Unbound optional arguments are ignored. */
void
gdbscm_parse_function_args (const char *func_name,
int beginning_arg_pos,
const SCM *keywords,
const char *format, ...)
{
va_list args;
va_start (args, format);
gdbscm_wrap (gdbscm_parse_function_args_1, func_name,
beginning_arg_pos, keywords, format, args);
va_end (args);
}
/* Return longest L as a scheme object. */