Re: Bugs in ecpg's macro mechanism

Andres Freund <andres@anarazel.de> writes:
> On 2024-04-15 17:48:32 -0400, Tom Lane wrote:
>> But I have no idea about making it work in meson.  Any suggestions?

> So you just want to compile define.c twice? The below should suffice:

> -  'define': ['-DCMDLINESYM=123'],
> +  'define': ['-DCMDLINESYM=123', files('define.pgc')],

Ah, thanks.  I guess this depends on getopt_long reordering arguments
(since the "-o outfile" bit will come later).  That is safe enough
in HEAD since 411b72034, but it might fail on weird platforms in v16.
How much do we care about that?  (We can avoid that hazard in the
makefile build easily enough.)

> I assume that was just an test hack, because it leads to the build failing
> because of main being duplicated. But it'd work the same with another, "non
> overlapping", file.

Yeah, I hadn't actually worked through what to do in detail.
Here's a v2 that adds that testing.  I also added some more
user-facing doco, and fixed a small memory leak that I noted
from valgrind testing.  (It's hardly the only one in ecpg,
but it was easy to fix as part of this patch.)

            regards, tom lane

From 10181143871d2fd927d8119771ecba38bb51951d Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Mon, 15 Apr 2024 20:37:50 -0400
Subject: [PATCH v2] Fix assorted bugs in ecpg's macro mechanism.

The code associated with EXEC SQL DEFINE was unreadable and full of
bugs, notably:

* it'd attempt to free a non-malloced string if the ecpg program
tries to redefine a macro that was defined on the command line;

* possible memory stomp if user writes "-D=foo";

* undef'ing or redefining a macro defined on the command line would
change the state visible to the next file, when multiple files are
specified on the command line;

* missing "break" in defining a new macro meant that redefinition
of an existing name would cause an extra entry to be added to the
definition list.  While not immediately harmful, a subsequent undef
would result in the prior entry becoming visible again.

* The interactions with input buffering are subtle and were entirely
undocumented.

It's not that surprising that we hadn't noticed these bugs,
because there was no test coverage at all of either the -D
command line switch or multiple input files.  This patch adds
such coverage (in a rather hacky way I guess).

In addition to the code bugs, the user documentation was confused
about whether the -D switch defines a C macro or an ecpg one, and
it failed to mention that you can write "-Dsymbol=value".

Discussion: https://postgr.es/m/998011.1713217712@sss.pgh.pa.us
---
 doc/src/sgml/ecpg.sgml                        |   8 ++
 doc/src/sgml/ref/ecpg-ref.sgml                |   6 +-
 src/interfaces/ecpg/preproc/ecpg.c            |  79 ++++++-----
 src/interfaces/ecpg/preproc/pgc.l             | 127 ++++++++++++------
 src/interfaces/ecpg/preproc/type.h            |  21 ++-
 .../ecpg/test/expected/sql-define.c           |  65 ++++++++-
 .../ecpg/test/expected/sql-define.stderr      |  24 ++++
 .../ecpg/test/expected/sql-define.stdout      |   3 +
 src/interfaces/ecpg/test/sql/Makefile         |   3 +
 src/interfaces/ecpg/test/sql/define.pgc       |  25 ++++
 .../ecpg/test/sql/define_prelim.pgc           |   6 +
 src/interfaces/ecpg/test/sql/meson.build      |   1 +
 12 files changed, 288 insertions(+), 80 deletions(-)
 create mode 100644 src/interfaces/ecpg/test/sql/define_prelim.pgc

diff --git a/doc/src/sgml/ecpg.sgml b/doc/src/sgml/ecpg.sgml
index b332aa435d..e7a53f3c9d 100644
--- a/doc/src/sgml/ecpg.sgml
+++ b/doc/src/sgml/ecpg.sgml
@@ -5793,6 +5793,14 @@ EXEC SQL UPDATE Tbl SET col = MYNUMBER;
     embedded SQL query because in this case the embedded SQL precompiler is not
     able to see this declaration.
    </para>
+
+   <para>
+    If multiple input files are named on the <command>ecpg</command>
+    preprocessor's command line, the effects of <literal>EXEC SQL
+    DEFINE</literal> and <literal>EXEC SQL UNDEF</literal> do not carry
+    across files: each file starts with only the symbols defined
+    by <option>-D</option> switches on the command line.
+   </para>
   </sect2>

   <sect2 id="ecpg-ifdef">
diff --git a/doc/src/sgml/ref/ecpg-ref.sgml b/doc/src/sgml/ref/ecpg-ref.sgml
index f3b6034f42..43f2d8bdaa 100644
--- a/doc/src/sgml/ref/ecpg-ref.sgml
+++ b/doc/src/sgml/ref/ecpg-ref.sgml
@@ -93,10 +93,12 @@ PostgreSQL documentation
     </varlistentry>

     <varlistentry>
-     <term><option>-D <replaceable>symbol</replaceable></option></term>
+     <term><option>-D <replaceable>symbol</replaceable>[=<replaceable>value</replaceable>]</option></term>
      <listitem>
       <para>
-       Define a C preprocessor symbol.
+       Define a preprocessor symbol, equivalently to the <command>EXEC SQL
+       DEFINE</command> directive.  If no <replaceable>value</replaceable> is
+       specified, the symbol is defined with the value <literal>1</literal>.
       </para>
      </listitem>
     </varlistentry>
diff --git a/src/interfaces/ecpg/preproc/ecpg.c b/src/interfaces/ecpg/preproc/ecpg.c
index 93e66fc60f..cbdc7866cd 100644
--- a/src/interfaces/ecpg/preproc/ecpg.c
+++ b/src/interfaces/ecpg/preproc/ecpg.c
@@ -82,35 +82,46 @@ add_include_path(char *path)
     }
 }

+/*
+ * Process a command line -D switch
+ */
 static void
 add_preprocessor_define(char *define)
 {
-    struct _defines *pd = defines;
-    char       *ptr,
-               *define_copy = mm_strdup(define);
+    /* copy the argument to avoid relying on argv storage */
+    char       *define_copy = mm_strdup(define);
+    char       *ptr;
+    struct _defines *newdef;

-    defines = mm_alloc(sizeof(struct _defines));
+    newdef = mm_alloc(sizeof(struct _defines));

     /* look for = sign */
     ptr = strchr(define_copy, '=');
     if (ptr != NULL)
     {
+        /* symbol has a value */
         char       *tmp;

-        /* symbol has a value */
-        for (tmp = ptr - 1; *tmp == ' '; tmp--);
+        /* strip any spaces between name and '=' */
+        for (tmp = ptr - 1; tmp >= define_copy && *tmp == ' '; tmp--);
         tmp[1] = '\0';
-        defines->olddef = define_copy;
-        defines->newdef = ptr + 1;
+
+        /*
+         * Note we don't bother to separately malloc cmdvalue; it will never
+         * be freed so that's not necessary.
+         */
+        newdef->cmdvalue = ptr + 1;
     }
     else
     {
-        defines->olddef = define_copy;
-        defines->newdef = mm_strdup("1");
+        /* define it as "1" */
+        newdef->cmdvalue = mm_strdup("1");
     }
-    defines->pertinent = true;
-    defines->used = NULL;
-    defines->next = pd;
+    newdef->name = define_copy;
+    newdef->value = mm_strdup(newdef->cmdvalue);
+    newdef->used = NULL;
+    newdef->next = defines;
+    defines = newdef;
 }

 #define ECPG_GETOPT_LONG_REGRESSION        1
@@ -348,6 +359,8 @@ main(int argc, char *const argv[])
             {
                 struct cursor *ptr;
                 struct _defines *defptr;
+                struct _defines *prevdefptr;
+                struct _defines *nextdefptr;
                 struct typedefs *typeptr;
                 struct declared_list *list;

@@ -385,28 +398,28 @@ main(int argc, char *const argv[])
                     free(this);
                 }

-                /* remove non-pertinent old defines as well */
-                while (defines && !defines->pertinent)
+                /* restore defines to their command-line state */
+                prevdefptr = NULL;
+                for (defptr = defines; defptr != NULL; defptr = nextdefptr)
                 {
-                    defptr = defines;
-                    defines = defines->next;
-
-                    free(defptr->newdef);
-                    free(defptr->olddef);
-                    free(defptr);
-                }
-
-                for (defptr = defines; defptr != NULL; defptr = defptr->next)
-                {
-                    struct _defines *this = defptr->next;
-
-                    if (this && !this->pertinent)
+                    nextdefptr = defptr->next;
+                    if (defptr->cmdvalue != NULL)
                     {
-                        defptr->next = this->next;
-
-                        free(this->newdef);
-                        free(this->olddef);
-                        free(this);
+                        /* keep it, resetting the value */
+                        free(defptr->value);
+                        defptr->value = mm_strdup(defptr->cmdvalue);
+                        prevdefptr = defptr;
+                    }
+                    else
+                    {
+                        /* remove it */
+                        if (prevdefptr != NULL)
+                            prevdefptr->next = nextdefptr;
+                        else
+                            defines = nextdefptr;
+                        free(defptr->name);
+                        free(defptr->value);
+                        free(defptr);
                     }
                 }

diff --git a/src/interfaces/ecpg/preproc/pgc.l b/src/interfaces/ecpg/preproc/pgc.l
index e56cd31d27..bcfbd0978b 100644
--- a/src/interfaces/ecpg/preproc/pgc.l
+++ b/src/interfaces/ecpg/preproc/pgc.l
@@ -69,7 +69,14 @@ char *token_start;
 static int state_before_str_start;
 static int state_before_str_stop;

-struct _yy_buffer
+/*
+ * State for handling include files and macro expansion.  We use a new
+ * flex input buffer for each level of include or macro, and create a
+ * struct _yy_buffer to remember the previous level.  There is not a struct
+ * for the currently active input source; that state is kept in the global
+ * variables YY_CURRENT_BUFFER, yylineno, and input_filename.
+ */
+static struct _yy_buffer
 {
     YY_BUFFER_STATE        buffer;
     long                lineno;
@@ -77,8 +84,6 @@ struct _yy_buffer
     struct _yy_buffer  *next;
 } *yy_buffer = NULL;

-static char *old;
-
 /*
  * Vars for handling ifdef/elif/endif constructs.  preproc_tos is the current
  * nesting depth of such constructs, and stacked_if_value[preproc_tos] is the
@@ -444,6 +449,8 @@ cppline            {space}*#([^i][A-Za-z]*|{if}|{ifdef}|{ifndef}|{import})((\/\*[^*/]*\*+

 %{
         /* code to execute during start of each call of yylex() */
+        char *newdefsymbol = NULL;
+
         token_start = NULL;
 %}

@@ -1010,6 +1017,7 @@ cppline            {space}*#([^i][A-Za-z]*|{if}|{ifdef}|{ifndef}|{import})((\/\*[^*/]*\*+
                 }

 {identifier}    {
+                    /* First check to see if it's a define symbol to expand */
                     if (!isdefine())
                     {
                         int        kwvalue;
@@ -1198,17 +1206,23 @@ cppline            {space}*#([^i][A-Za-z]*|{if}|{ifdef}|{ifndef}|{import})((\/\*[^*/]*\*+
                     yytext[i+1] = '\0';


-                    for (ptr = defines; ptr != NULL; ptr2 = ptr, ptr = ptr->next)
+                    /* Find and unset any matching define; should be only 1 */
+                    for (ptr = defines; ptr; ptr2 = ptr, ptr = ptr->next)
                     {
-                        if (strcmp(yytext, ptr->olddef) == 0)
+                        if (strcmp(yytext, ptr->name) == 0)
                         {
-                            if (ptr2 == NULL)
-                                defines = ptr->next;
-                            else
-                                ptr2->next = ptr->next;
-                            free(ptr->newdef);
-                            free(ptr->olddef);
-                            free(ptr);
+                            free(ptr->value);
+                            ptr->value = NULL;
+                            /* We cannot forget it if there's a cmdvalue */
+                            if (ptr->cmdvalue == NULL)
+                            {
+                                if (ptr2 == NULL)
+                                    defines = ptr->next;
+                                else
+                                    ptr2->next = ptr->next;
+                                free(ptr->name);
+                                free(ptr);
+                            }
                             break;
                         }
                     }
@@ -1413,11 +1427,17 @@ cppline            {space}*#([^i][A-Za-z]*|{if}|{ifdef}|{ifndef}|{import})((\/\*[^*/]*\*+
                             ;
                         yytext[i+1] = '\0';

-                        for (defptr = defines;
-                             defptr != NULL &&
-                             strcmp(yytext, defptr->olddef) != 0;
-                             defptr = defptr->next)
-                            /* skip */ ;
+                        /* Does a definition exist? */
+                        for (defptr = defines; defptr; defptr = defptr->next)
+                        {
+                            if (strcmp(yytext, defptr->name) == 0)
+                            {
+                                /* Found it, but is it currently undefined? */
+                                if (defptr->value == NULL)
+                                    defptr = NULL; /* pretend it's not found */
+                                break;
+                            }
+                        }

                         this_active = (defptr ? ifcond : !ifcond);
                         stacked_if_value[preproc_tos].active =
@@ -1438,7 +1458,7 @@ cppline            {space}*#([^i][A-Za-z]*|{if}|{ifdef}|{ifndef}|{import})((\/\*[^*/]*\*+
                 yyterminate();
             }
 <def_ident>{identifier} {
-                old = mm_strdup(yytext);
+                newdefsymbol = mm_strdup(yytext);
                 BEGIN(def);
                 startlit();
             }
@@ -1447,26 +1467,31 @@ cppline            {space}*#([^i][A-Za-z]*|{if}|{ifdef}|{ifndef}|{import})((\/\*[^*/]*\*+
                 yyterminate();
             }
 <def>{space}*";"    {
-                        struct _defines *ptr, *this;
+                        struct _defines *ptr;

+                        /* Does it already exist? */
                         for (ptr = defines; ptr != NULL; ptr = ptr->next)
                         {
-                             if (strcmp(old, ptr->olddef) == 0)
-                             {
-                                free(ptr->newdef);
-                                ptr->newdef = mm_strdup(literalbuf);
-                             }
+                            if (strcmp(newdefsymbol, ptr->name) == 0)
+                            {
+                                free(ptr->value);
+                                ptr->value = mm_strdup(literalbuf);
+                                /* Don't leak newdefsymbol */
+                                free(newdefsymbol);
+                                break;
+                            }
                         }
                         if (ptr == NULL)
                         {
-                            this = (struct _defines *) mm_alloc(sizeof(struct _defines));
-
-                            /* initial definition */
-                            this->olddef = old;
-                            this->newdef = mm_strdup(literalbuf);
-                            this->next = defines;
-                            this->used = NULL;
-                            defines = this;
+                            /* Not present, make a new entry */
+                            ptr = (struct _defines *) mm_alloc(sizeof(struct _defines));
+
+                            ptr->name = newdefsymbol;
+                            ptr->value = mm_strdup(literalbuf);
+                            ptr->cmdvalue = NULL;
+                            ptr->used = NULL;
+                            ptr->next = defines;
+                            defines = ptr;
                         }

                         BEGIN(C);
@@ -1483,6 +1508,7 @@ cppline            {space}*#([^i][A-Za-z]*|{if}|{ifdef}|{ifndef}|{import})((\/\*[^*/]*\*+
 <<EOF>>                {
                     if (yy_buffer == NULL)
                     {
+                        /* No more input */
                         if (preproc_tos > 0)
                         {
                             preproc_tos = 0;
@@ -1492,16 +1518,20 @@ cppline            {space}*#([^i][A-Za-z]*|{if}|{ifdef}|{ifndef}|{import})((\/\*[^*/]*\*+
                     }
                     else
                     {
+                        /* Revert to previous input source */
                         struct _yy_buffer *yb = yy_buffer;
                         int i;
                         struct _defines *ptr;

+                        /* Check to see if we are exiting a macro value */
                         for (ptr = defines; ptr; ptr = ptr->next)
+                        {
                             if (ptr->used == yy_buffer)
                             {
                                 ptr->used = NULL;
-                                break;
+                                break; /* there can't be multiple matches */
                             }
+                        }

                         if (yyin != NULL)
                             fclose(yyin);
@@ -1727,15 +1757,24 @@ ecpg_isspace(char ch)
     return false;
 }

-static bool isdefine(void)
+/*
+ * If yytext matches a define symbol, begin scanning the symbol's value
+ * and return true
+ */
+static bool
+isdefine(void)
 {
     struct _defines *ptr;

     /* is it a define? */
     for (ptr = defines; ptr; ptr = ptr->next)
     {
-        if (strcmp(yytext, ptr->olddef) == 0 && ptr->used == NULL)
+        /* notice we do not match anything being actively expanded */
+        if (strcmp(yytext, ptr->name) == 0 &&
+            ptr->value != NULL &&
+            ptr->used == NULL)
         {
+            /* Save state associated with the current buffer */
             struct _yy_buffer *yb;

             yb = mm_alloc(sizeof(struct _yy_buffer));
@@ -1744,10 +1783,17 @@ static bool isdefine(void)
             yb->lineno = yylineno;
             yb->filename = mm_strdup(input_filename);
             yb->next = yy_buffer;
+            yy_buffer = yb;

-            ptr->used = yy_buffer = yb;
+            /* Mark symbol as being actively expanded */
+            ptr->used = yb;

-            yy_scan_string(ptr->newdef);
+            /*
+             * We use yy_scan_string which will copy the value, so there's
+             * no need to worry about a possible undef happening while we
+             * are still scanning it.
+             */
+            yy_scan_string(ptr->value);
             return true;
         }
     }
@@ -1755,7 +1801,12 @@ static bool isdefine(void)
     return false;
 }

-static bool isinformixdefine(void)
+/*
+ * Handle replacement of INFORMIX built-in defines.  This works just
+ * like isdefine() except for the source of the string to scan.
+ */
+static bool
+isinformixdefine(void)
 {
     const char *new = NULL;

diff --git a/src/interfaces/ecpg/preproc/type.h b/src/interfaces/ecpg/preproc/type.h
index 5935cd7473..45290e815b 100644
--- a/src/interfaces/ecpg/preproc/type.h
+++ b/src/interfaces/ecpg/preproc/type.h
@@ -163,13 +163,24 @@ struct typedefs
     struct typedefs *next;
 };

+/*
+ * Info about a defined symbol (macro), coming from a -D command line switch
+ * or a define command in the program.  These are stored in a simple list.
+ * Because ecpg supports compiling multiple files per run, we have to remember
+ * the command-line definitions and be able to revert to those; this motivates
+ * storing cmdvalue separately from value.
+ * used is NULL unless we are currently expanding the macro, in which case
+ * it points to the buffer before the one scanning the macro; we reset it
+ * to NULL upon returning to that buffer.  This is used to prevent recursive
+ * expansion of the macro.
+ */
 struct _defines
 {
-    char       *olddef;
-    char       *newdef;
-    int            pertinent;
-    void       *used;
-    struct _defines *next;
+    char       *name;            /* symbol name (malloc'd string) */
+    char       *value;            /* current value, or NULL if undefined */
+    char       *cmdvalue;        /* value set on command line, or NULL */
+    void       *used;            /* buffer pointer, or NULL */
+    struct _defines *next;        /* list link */
 };

 /* This is a linked list of the variable names and types. */
diff --git a/src/interfaces/ecpg/test/expected/sql-define.c b/src/interfaces/ecpg/test/expected/sql-define.c
index 29583ecd74..e97caec5b0 100644
--- a/src/interfaces/ecpg/test/expected/sql-define.c
+++ b/src/interfaces/ecpg/test/expected/sql-define.c
@@ -6,6 +6,21 @@
 /* End of automatic include section */
 #define ECPGdebug(X,Y) ECPGdebug((X)+100,(Y))

+#line 1 "define_prelim.pgc"
+/*
+ * Test that the effects of these commands don't carry over to the next
+ * file named on the ecpg command line.
+ */
+
+
+/* Processed by ecpg (regression mode) */
+/* These include files are added by the preprocessor */
+#include <ecpglib.h>
+#include <ecpgerrno.h>
+#include <sqlca.h>
+/* End of automatic include section */
+#define ECPGdebug(X,Y) ECPGdebug((X)+100,(Y))
+
 #line 1 "define.pgc"

 #line 1 "sqlca.h"
@@ -195,11 +210,57 @@ if (sqlca.sqlcode < 0) sqlprint ( );}



+   /* test handling of a macro defined on the command line */
+   { ECPGdo(__LINE__, 0, 1, NULL, 0, ECPGst_normal, "select 123", ECPGt_EOIT,
+    ECPGt_int,&(i),(long)1,(long)1,sizeof(int),
+    ECPGt_NO_INDICATOR, NULL , 0L, 0L, 0L, ECPGt_EORT);
+#line 57 "define.pgc"
+
+if (sqlca.sqlcode < 0) sqlprint ( );}
+#line 57 "define.pgc"
+
+   printf("original CMDLINESYM: %d\n", i);
+
+
+
+   { ECPGdo(__LINE__, 0, 1, NULL, 0, ECPGst_normal, "select 42", ECPGt_EOIT,
+    ECPGt_int,&(i),(long)1,(long)1,sizeof(int),
+    ECPGt_NO_INDICATOR, NULL , 0L, 0L, 0L, ECPGt_EORT);
+#line 62 "define.pgc"
+
+if (sqlca.sqlcode < 0) sqlprint ( );}
+#line 62 "define.pgc"
+
+   printf("redefined CMDLINESYM: %d\n", i);
+
+
+
+   { ECPGdo(__LINE__, 0, 1, NULL, 0, ECPGst_normal, "select 43", ECPGt_EOIT,
+    ECPGt_int,&(i),(long)1,(long)1,sizeof(int),
+    ECPGt_NO_INDICATOR, NULL , 0L, 0L, 0L, ECPGt_EORT);
+#line 67 "define.pgc"
+
+if (sqlca.sqlcode < 0) sqlprint ( );}
+#line 67 "define.pgc"
+
+   printf("redefined CMDLINESYM: %d\n", i);
+
+
+
+
+
+
+
+   /* this macro should not have carried over from define_prelim.pgc */
+
+
+
+
    { ECPGdisconnect(__LINE__, "CURRENT");
-#line 56 "define.pgc"
+#line 81 "define.pgc"

 if (sqlca.sqlcode < 0) sqlprint ( );}
-#line 56 "define.pgc"
+#line 81 "define.pgc"

    return 0;
 }
diff --git a/src/interfaces/ecpg/test/expected/sql-define.stderr b/src/interfaces/ecpg/test/expected/sql-define.stderr
index 20601b63cf..c4da9927e8 100644
--- a/src/interfaces/ecpg/test/expected/sql-define.stderr
+++ b/src/interfaces/ecpg/test/expected/sql-define.stderr
@@ -48,5 +48,29 @@
 [NO_PID]: sqlca: code: 0, state: 00000
 [NO_PID]: ecpg_process_output on line 53: OK: SET
 [NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 57: query: select 123; with 0 parameter(s) on connection ecpg1_regression
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 57: using PQexec
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_process_output on line 57: correctly got 1 tuples with 1 fields
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_get_data on line 57: RESULT: 123 offset: -1; array: no
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 62: query: select 42; with 0 parameter(s) on connection ecpg1_regression
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 62: using PQexec
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_process_output on line 62: correctly got 1 tuples with 1 fields
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_get_data on line 62: RESULT: 42 offset: -1; array: no
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 67: query: select 43; with 0 parameter(s) on connection ecpg1_regression
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 67: using PQexec
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_process_output on line 67: correctly got 1 tuples with 1 fields
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_get_data on line 67: RESULT: 43 offset: -1; array: no
+[NO_PID]: sqlca: code: 0, state: 00000
 [NO_PID]: ecpg_finish: connection ecpg1_regression closed
 [NO_PID]: sqlca: code: 0, state: 00000
diff --git a/src/interfaces/ecpg/test/expected/sql-define.stdout b/src/interfaces/ecpg/test/expected/sql-define.stdout
index 864cd850bf..eaddc7f8c3 100644
--- a/src/interfaces/ecpg/test/expected/sql-define.stdout
+++ b/src/interfaces/ecpg/test/expected/sql-define.stdout
@@ -1 +1,4 @@
 i: 1, s: 29-abcdef
+original CMDLINESYM: 123
+redefined CMDLINESYM: 42
+redefined CMDLINESYM: 43
diff --git a/src/interfaces/ecpg/test/sql/Makefile b/src/interfaces/ecpg/test/sql/Makefile
index 7f032659b9..3ff190a523 100644
--- a/src/interfaces/ecpg/test/sql/Makefile
+++ b/src/interfaces/ecpg/test/sql/Makefile
@@ -34,5 +34,8 @@ TESTS = array array.c \

 all: $(TESTS)

+define.c: define.pgc define_prelim.pgc $(ECPG_TEST_DEPENDENCIES)
+    $(ECPG) -DCMDLINESYM=123 -o $@ $(srcdir)/define_prelim.pgc $<
+
 oldexec.c: oldexec.pgc $(ECPG_TEST_DEPENDENCIES)
     $(ECPG) -r questionmarks -o $@ $<
diff --git a/src/interfaces/ecpg/test/sql/define.pgc b/src/interfaces/ecpg/test/sql/define.pgc
index ed58a4bde0..83f328df46 100644
--- a/src/interfaces/ecpg/test/sql/define.pgc
+++ b/src/interfaces/ecpg/test/sql/define.pgc
@@ -53,6 +53,31 @@ int main(void)
    exec sql SET TIMEZONE TO TZVAR;
    exec sql endif;

+   /* test handling of a macro defined on the command line */
+   exec sql select CMDLINESYM INTO :i;
+   printf("original CMDLINESYM: %d\n", i);
+
+   exec sql define CMDLINESYM 42;
+
+   exec sql select CMDLINESYM INTO :i;
+   printf("redefined CMDLINESYM: %d\n", i);
+
+   exec sql define CMDLINESYM 43;
+
+   exec sql select CMDLINESYM INTO :i;
+   printf("redefined CMDLINESYM: %d\n", i);
+
+   exec sql undef CMDLINESYM;
+
+   exec sql ifdef CMDLINESYM;
+   exec sql insert into test values (NUMBER, 'no string');
+   exec sql endif;
+
+   /* this macro should not have carried over from define_prelim.pgc */
+   exec sql ifdef NONCMDLINESYM;
+   exec sql insert into test values (NUMBER, 'no string');
+   exec sql endif;
+
    exec sql disconnect;
    return 0;
 }
diff --git a/src/interfaces/ecpg/test/sql/define_prelim.pgc b/src/interfaces/ecpg/test/sql/define_prelim.pgc
new file mode 100644
index 0000000000..7a984f74c8
--- /dev/null
+++ b/src/interfaces/ecpg/test/sql/define_prelim.pgc
@@ -0,0 +1,6 @@
+/*
+ * Test that the effects of these commands don't carry over to the next
+ * file named on the ecpg command line.
+ */
+exec sql define CMDLINESYM 999;
+exec sql define NONCMDLINESYM 1234;
diff --git a/src/interfaces/ecpg/test/sql/meson.build b/src/interfaces/ecpg/test/sql/meson.build
index 88a3acb9af..4da6e19f5f 100644
--- a/src/interfaces/ecpg/test/sql/meson.build
+++ b/src/interfaces/ecpg/test/sql/meson.build
@@ -31,6 +31,7 @@ pgc_files = [
 ]

 pgc_extra_flags = {
+  'define': ['-DCMDLINESYM=123', files('define_prelim.pgc')],
   'oldexec': ['-r', 'questionmarks'],
 }

--
2.39.3