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add const qualifiers to sys_var::value_ptr functions and fix const casts

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This is important since Sys_var_typelib and its descendants return
pointers to constant symbols from *_value_ptr, which are situated in
write-protected-memory.

* functions const-qualified:
  - value_ptr
  - session_value_ptr
  - global_value_ptr
  - default_value_ptr
  - Sys_var_vers_asof::value_ptr
  - other minor private ones

* remove C-style typecasts when it discards qualifiers
This commit is contained in:
Nikita Malyavin
2019-07-18 03:15:55 +10:00
parent c6bff46958
commit 6ed47508c8
7 changed files with 198 additions and 164 deletions
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70
sql/sql_show.cc
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@ -3568,6 +3568,28 @@ void remove_status_vars(SHOW_VAR *list)
}
}
/**
A union holding a pointer to a type that can be referred by a status variable.
*/
union Any_pointer {
const void *as_void;
const uchar *as_uchar;
const char *as_char;
const char ** as_charptr;
const double *as_double;
const int * as_int;
const uint * as_uint;
const long *as_long;
const longlong *as_longlong;
const bool *as_bool;
const my_bool *as_my_bool;
const sys_var *as_sys_var;
const system_status_var *as_system_status_var;
const ha_rows *as_ha_rows;
const LEX_STRING *as_lex_cstring;
const SHOW_COMP_OPTION *as_show_comp_options;
intptr as_intptr;
};
/**
@brief Returns the value of a system or a status variable.
@ -3592,16 +3614,18 @@ const char* get_one_variable(THD *thd,
const CHARSET_INFO **charset, char *buff,
size_t *length)
{
void *value= variable->value;
Any_pointer value, status_var_value;
value.as_void= variable->value;
status_var_value.as_system_status_var= status_var;
const char *pos= buff;
const char *end= buff;
if (show_type == SHOW_SYS)
{
sys_var *var= (sys_var *) value;
const sys_var *var= value.as_sys_var;
show_type= var->show_type();
value= var->value_ptr(thd, value_type, &null_clex_str);
value.as_uchar= var->value_ptr(thd, value_type, &null_clex_str);
*charset= var->charset(thd);
}
@ -3611,66 +3635,65 @@ const char* get_one_variable(THD *thd,
*/
switch (show_type) {
case SHOW_DOUBLE_STATUS:
value= ((char *) status_var + (intptr) value);
value.as_char= status_var_value.as_char + value.as_intptr;
/* fall through */
case SHOW_DOUBLE:
/* 6 is the default precision for '%f' in sprintf() */
end= buff + my_fcvt(*(double *) value, 6, buff, NULL);
end= buff + my_fcvt(*value.as_double, 6, buff, NULL);
break;
case SHOW_LONG_STATUS:
value= ((char *) status_var + (intptr) value);
value.as_char= status_var_value.as_char + value.as_intptr;
/* fall through */
case SHOW_ULONG:
case SHOW_LONG_NOFLUSH: // the difference lies in refresh_status()
end= int10_to_str(*(long*) value, buff, 10);
end= int10_to_str(*value.as_long, buff, 10);
break;
case SHOW_LONGLONG_STATUS:
value= ((char *) status_var + (intptr) value);
value.as_char= status_var_value.as_char + value.as_intptr;
/* fall through */
case SHOW_ULONGLONG:
end= longlong10_to_str(*(longlong*) value, buff, 10);
end= longlong10_to_str(*value.as_longlong, buff, 10);
break;
case SHOW_HA_ROWS:
end= longlong10_to_str((longlong) *(ha_rows*) value, buff, 10);
end= longlong10_to_str((longlong) *value.as_ha_rows, buff, 10);
break;
case SHOW_BOOL:
end= strmov(buff, *(bool*) value ? "ON" : "OFF");
end= strmov(buff, *value.as_bool ? "ON" : "OFF");
break;
case SHOW_MY_BOOL:
end= strmov(buff, *(my_bool*) value ? "ON" : "OFF");
end= strmov(buff, *value.as_my_bool ? "ON" : "OFF");
break;
case SHOW_UINT32_STATUS:
value= ((char *) status_var + (intptr) value);
value.as_char= status_var_value.as_char + value.as_intptr;
/* fall through */
case SHOW_UINT:
end= int10_to_str((long) *(uint*) value, buff, 10);
end= int10_to_str((long) *value.as_uint, buff, 10);
break;
case SHOW_SINT:
end= int10_to_str((long) *(int*) value, buff, -10);
end= int10_to_str((long) *value.as_int, buff, -10);
break;
case SHOW_SLONG:
end= int10_to_str(*(long*) value, buff, -10);
end= int10_to_str(*value.as_long, buff, -10);
break;
case SHOW_SLONGLONG:
end= longlong10_to_str(*(longlong*) value, buff, -10);
end= longlong10_to_str(*value.as_longlong, buff, -10);
break;
case SHOW_HAVE:
{
SHOW_COMP_OPTION tmp= *(SHOW_COMP_OPTION*) value;
pos= show_comp_option_name[(int) tmp];
pos= show_comp_option_name[(int) *value.as_show_comp_options];
end= strend(pos);
break;
}
case SHOW_CHAR:
{
if (!(pos= (char*)value))
if (!(pos= value.as_char))
pos= "";
end= strend(pos);
break;
}
case SHOW_CHAR_PTR:
{
if (!(pos= *(char**) value))
if (!(pos= *value.as_charptr))
pos= "";
end= strend(pos);
@ -3678,11 +3701,10 @@ const char* get_one_variable(THD *thd,
}
case SHOW_LEX_STRING:
{
LEX_STRING *ls=(LEX_STRING*)value;
if (!(pos= ls->str))
if (!(pos= value.as_lex_cstring->str))
end= pos= "";
else
end= pos + ls->length;
end= pos + value.as_lex_cstring->length;
break;
}
case SHOW_UNDEF: