Add PGTYPESchar_free() to avoid cross-module problems on Windows.

On Windows, it is sometimes important for corresponding malloc() and
free() calls to be made from the same DLL, since some build options can
result in multiple allocators being active at the same time.  For that
reason we already provided PQfreemem().  This commit adds a similar
function for freeing string results allocated by the pgtypes library.

Author: Takayuki Tsunakawa
Reviewed-by: Kyotaro Horiguchi
Discussion: https://postgr.es/m/0A3221C70F24FB45833433255569204D1F8AD5D6%40G01JPEXMBYT05

Author: macdice

doc/src/sgml/ecpg.sgml

@@ -1951,11 +1951,23 @@ EXEC SQL SELECT started, duration INTO :ts1, :iv1 FROM datetbl WHERE d=:date1;
 PGTYPEStimestamp_add_interval(&ts1, &iv1, &tsout);
 out = PGTYPEStimestamp_to_asc(&tsout);
 printf("Started + duration: %s\n", out);
-free(out);
+PGTYPESchar_free(out);
 ]]>
 </programlisting>
   </para>
 
+  <sect2 id="ecpg-pgtypes-cstrings">
+   <title>Character Strings</title>
+   <para>
+   Some functions such as <function>PGTYPESnumeric_to_asc</function> return
+   a pointer to a freshly allocated character string. These results should be
+   freed with <function>PGTYPESchar_free</function> instead of
+   <function>free</function>. (This is important only on Windows, where
+   memory allocation and release sometimes need to be done by the same
+   library.)
+   </para>
+  </sect2>
+
   <sect2 id="ecpg-pgtypes-numeric">
    <title>The numeric Type</title>
    <para>
@@ -2029,6 +2041,7 @@ char *PGTYPESnumeric_to_asc(numeric *num, int dscale);
 </synopsis>
        The numeric value will be printed with <literal>dscale</literal> decimal
        digits, with rounding applied if necessary.
+       The result must be freed with <function>PGTYPESchar_free()</function>.
       </para>
      </listitem>
     </varlistentry>
@@ -2419,6 +2432,7 @@ char *PGTYPESdate_to_asc(date dDate);
         The function receives the date <literal>dDate</literal> as its only parameter.
         It will output the date in the form <literal>1999-01-18</literal>, i.e., in the
         <literal>YYYY-MM-DD</literal> format.
+        The result must be freed with <function>PGTYPESchar_free()</function>.
        </para>
       </listitem>
      </varlistentry>
@@ -2841,6 +2855,7 @@ char *PGTYPEStimestamp_to_asc(timestamp tstamp);
         The function receives the timestamp <literal>tstamp</literal> as
         its only argument and returns an allocated string that contains the
         textual representation of the timestamp.
+        The result must be freed with <function>PGTYPESchar_free()</function>.
        </para>
       </listitem>
      </varlistentry>
@@ -3349,6 +3364,7 @@ char *PGTYPESinterval_to_asc(interval *span);
         The function converts the interval variable that <literal>span</literal>
         points to into a C char*. The output looks like this example:
         <literal>@ 1 day 12 hours 59 mins 10 secs</literal>.
+        The result must be freed with <function>PGTYPESchar_free()</function>.
        </para>
       </listitem>
      </varlistentry>

src/interfaces/ecpg/include/Makefile

@@ -14,7 +14,7 @@ install: all installdirs install-headers
 
 .PHONY: install-headers
 ecpg_headers = ecpgerrno.h ecpglib.h ecpgtype.h sqlca.h sql3types.h ecpg_informix.h \
-	pgtypes_error.h pgtypes_numeric.h pgtypes_timestamp.h pgtypes_date.h pgtypes_interval.h \
+	pgtypes_error.h pgtypes_numeric.h pgtypes_timestamp.h pgtypes_date.h pgtypes_interval.h pgtypes.h \
 	sqlda.h sqlda-compat.h sqlda-native.h
 informix_headers = datetime.h decimal.h sqltypes.h
 

src/interfaces/ecpg/include/pgtypes.h

@@ -0,0 +1,17 @@
+/* src/interfaces/ecpg/include/pgtypes.h */
+
+#ifndef PGTYPES_H
+#define PGTYPES_H
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+extern void PGTYPESchar_free(char *ptr);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif							/* PGTYPES_H */

src/interfaces/ecpg/include/pgtypes_date.h

@@ -3,6 +3,7 @@
 #ifndef PGTYPES_DATETIME
 #define PGTYPES_DATETIME
 
+#include <pgtypes.h>
 #include <pgtypes_timestamp.h>
 
 typedef long date;

src/interfaces/ecpg/include/pgtypes_interval.h

@@ -4,6 +4,7 @@
 #define PGTYPES_INTERVAL
 
 #include <ecpg_config.h>
+#include <pgtypes.h>
 
 #ifndef C_H
 

src/interfaces/ecpg/include/pgtypes_numeric.h

@@ -1,6 +1,8 @@
 #ifndef PGTYPES_NUMERIC
 #define PGTYPES_NUMERIC
 
+#include <pgtypes.h>
+
 #define NUMERIC_POS						0x0000
 #define NUMERIC_NEG						0x4000
 #define NUMERIC_NAN						0xC000

src/interfaces/ecpg/include/pgtypes_timestamp.h

@@ -3,6 +3,7 @@
 #ifndef PGTYPES_TIMESTAMP
 #define PGTYPES_TIMESTAMP
 
+#include <pgtypes.h>
 /* pgtypes_interval.h includes ecpg_config.h */
 #include <pgtypes_interval.h>
 

src/interfaces/ecpg/pgtypeslib/common.c

@@ -3,6 +3,7 @@
 #include "postgres_fe.h"
 
 #include "extern.h"
+#include "pgtypes.h"
 
 /* Return value is zero-filled. */
 char *
@@ -136,3 +137,12 @@ pgtypes_fmt_replace(union un_fmt_comb replace_val, int replace_type, char **outp
 	}
 	return 0;
 }
+
+/* Functions declared in pgtypes.h. */
+
+/* Just frees memory (mostly needed for Windows) */
+void
+PGTYPESchar_free(char *ptr)
+{
+	free(ptr);
+}

src/interfaces/ecpg/pgtypeslib/exports.txt

@@ -45,3 +45,4 @@ PGTYPEStimestamp_from_asc       42
 PGTYPEStimestamp_sub            43
 PGTYPEStimestamp_sub_interval   44
 PGTYPEStimestamp_to_asc         45
+PGTYPESchar_free                46