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Allow nested use of PR_SaveParams()

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PR_SaveParams() is required for implementing the +initialize diversion
used by Objective-QuakeC because builtins do not have local def spaces
(of course, a normal stack calling convention would help). However, it
is entirely possible for a call to +initialize to trigger another call
to +initialize, thus the need for stacking parameter stashes. As a
bonus, this implementation cleans up some fields in progs_t.
This commit is contained in:
Bill Currie 2020-02-25 14:30:26 +09:00
parent 99c818adcc
commit 9bb68f2d8c
4 changed files with 71 additions and 27 deletions
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59
include/QF/progs.h
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@ -91,15 +91,63 @@ void PR_RunError (progs_t *pr, const char *error, ...) __attribute__((format(pri
(pr)->pr_params[1] = (pr)->pr_real_params[1]; \
} while (0)
/** Save the current parameters.
\param pr pointer to ::progs_t VM struct
/** \name Detouring Function Calls
These functions allow a builtin function that uses PR_CallFunction() to
safely insert a call to another VM function. The +initialize diversion
required by Objective-QuakeC uses this.
PR_PushFrame (pr);
__auto_type params = PR_SaveParams (pr);
... set up parameters to detour_function
PR_ExecuteProgram (pr, detour_function)
PR_RestoreParams (pr, params);
PR_PopFrame (pr);
*/
void PR_SaveParams (progs_t *pr);
///@{
typedef struct pr_stashed_params_s {
pr_type_t *param_ptrs[2];
int argc;
pr_type_t params[1];
} pr_stashed_params_t;
/** Save the current parameters to the provided stash.
\warning The memory for the parameter stash is allocated using
alloca().
\param pr pointer to ::progs_t VM struct
\return Pointer to a newly allocated and initialized parameter
stash that has the current parameters saved to it.
\hideinitializer
*/
#define PR_SaveParams(pr) \
_PR_SaveParams((pr), \
alloca (field_offset (pr_stashed_params_t, \
params[(pr)->pr_argc \
* (pr)->pr_param_size])))
/** [INTERNAL] Save the current parameters to the provided stash.
\warning Requires \a params to be correctly allocated. Use
PR_SaveParams instead as it will create a suitable stash for
saving the parameters.
\param pr pointer to ::progs_t VM struct
\param params location to save the parameters, must be of adequade size
to hold \a pr_argc * \a pr_param_size words in \a params
\return \a params Allows the likes of:
__auto_type params = PR_SaveParams (pr);
*/
pr_stashed_params_t *_PR_SaveParams (progs_t *pr, pr_stashed_params_t *params);
/** Restore the parameters saved by PR_SaveParams().
\param pr pointer to ::progs_t VM struct
\param params pointer to stash created by PR_SaveParams()
*/
void PR_RestoreParams (progs_t *pr);
void PR_RestoreParams (progs_t *pr, pr_stashed_params_t *params);
///@}
/** Push an execution frame onto the VM stack. Saves current execution state.
\param pr pointer to ::progs_t VM struct
@ -1662,9 +1710,6 @@ struct progs_s {
pr_type_t *pr_return;
pr_type_t *pr_params[MAX_PARMS];
pr_type_t *pr_real_params[MAX_PARMS];
pr_type_t *pr_param_ptrs[2];
pr_type_t *pr_saved_params;
int pr_saved_argc;
int pr_param_size; ///< covers both params and return
int pr_param_alignment; ///< covers both params and return
///@}