ecpg: improve preprocessor's memory management.

Invent a notion of "local" storage that will automatically be
reclaimed at the end of each statement.  Use this for location
strings as well as other visibly short-lived data within the parser.

Also, make cat_str and make_str return local storage and not free
their inputs, which allows dispensing with a whole lot of retail
mm_strdup calls.  We do have to add some new ones in places where
a local-lifetime string needs to be added to a longer-lived data
structure, but on balance there are a lot less mm_strdup calls than
before.

In hopes of flushing out places where changes were necessary,
I changed YYLTYPE from "char *" to "const char *", which forced
const-ification of various function arguments that probably
should've been like that all along.

This still leaks somewhat more memory than v17, but that will be
cleaned up in future commits.

Discussion: https://postgr.es/m/2011420.1713493114@sss.pgh.pa.us

1 files changed, 19 insertions, 17 deletions

diff --git a/src/interfaces/ecpg/preproc/preproc_extern.h b/src/interfaces/ecpg/preproc/preproc_extern.h
index 29329ccd891..a60b0381fbb 100644
--- a/src/interfaces/ecpg/preproc/preproc_extern.h
+++ b/src/interfaces/ecpg/preproc/preproc_extern.h
@@ -13,12 +13,11 @@
 /* defines */
 
 #define STRUCT_DEPTH 128
-#define EMPTY mm_strdup("")
 
 /*
  * "Location tracking" support --- see ecpg.header for more comments.
  */
-typedef char *YYLTYPE;
+typedef const char *YYLTYPE;
 
 #define YYLTYPE_IS_DECLARED 1
 
@@ -82,22 +81,25 @@ extern int	base_yylex(void);
 extern void base_yyerror(const char *error);
 extern void *mm_alloc(size_t size);
 extern char *mm_strdup(const char *string);
-extern char *cat2_str(char *str1, char *str2);
+extern void *loc_alloc(size_t size);
+extern char *loc_strdup(const char *string);
+extern void reclaim_local_storage(void);
+extern char *cat2_str(const char *str1, const char *str2);
 extern char *cat_str(int count,...);
-extern char *make2_str(char *str1, char *str2);
-extern char *make3_str(char *str1, char *str2, char *str3);
+extern char *make2_str(const char *str1, const char *str2);
+extern char *make3_str(const char *str1, const char *str2, const char *str3);
 extern void mmerror(int error_code, enum errortype type, const char *error,...) pg_attribute_printf(3, 4);
 extern void mmfatal(int error_code, const char *error,...) pg_attribute_printf(2, 3) pg_attribute_noreturn();
-extern void output_get_descr_header(char *desc_name);
-extern void output_get_descr(char *desc_name, char *index);
-extern void output_set_descr_header(char *desc_name);
-extern void output_set_descr(char *desc_name, char *index);
-extern void push_assignment(char *var, enum ECPGdtype value);
-extern struct variable *find_variable(char *name);
+extern void output_get_descr_header(const char *desc_name);
+extern void output_get_descr(const char *desc_name, const char *index);
+extern void output_set_descr_header(const char *desc_name);
+extern void output_set_descr(const char *desc_name, const char *index);
+extern void push_assignment(const char *var, enum ECPGdtype value);
+extern struct variable *find_variable(const char *name);
 extern void whenever_action(int mode);
-extern void add_descriptor(char *name, char *connection);
-extern void drop_descriptor(char *name, char *connection);
-extern struct descriptor *lookup_descriptor(char *name, char *connection);
+extern void add_descriptor(const char *name, const char *connection);
+extern void drop_descriptor(const char *name, const char *connection);
+extern struct descriptor *lookup_descriptor(const char *name, const char *connection);
 extern struct variable *descriptor_variable(const char *name, int input);
 extern struct variable *sqlda_variable(const char *name);
 extern void add_variable_to_head(struct arguments **list,
@@ -109,9 +111,9 @@ extern void add_variable_to_tail(struct arguments **list,
 extern void remove_variable_from_list(struct arguments **list, struct variable *var);
 extern void dump_variables(struct arguments *list, int mode);
 extern struct typedefs *get_typedef(const char *name, bool noerror);
-extern void adjust_array(enum ECPGttype type_enum, char **dimension,
-						 char **length, char *type_dimension,
-						 char *type_index, int pointer_len,
+extern void adjust_array(enum ECPGttype type_enum, const char **dimension,
+						 const char **length, const char *type_dimension,
+						 const char *type_index, int pointer_len,
 						 bool type_definition);
 extern void reset_variables(void);
 extern void check_indicator(struct ECPGtype *var);