Arrange to supply declarations for strtoll/strtoull if needed.

Buildfarm member dromedary is still unhappy about the recently-added
ecpg "long long" tests.  The reason turns out to be that it includes
"-ansi" in its CFLAGS, and in their infinite wisdom Apple have decided
to hide the declarations of strtoll/strtoull in C89-compliant builds.
(I find it pretty curious that they hide those function declarations
when you can nonetheless declare a "long long" variable, but anyway
that is their behavior, both on dromedary's obsolete macOS version and
the newest and shiniest.)  As a result, gcc assumes these functions
return "int", leading naturally to wrong results.

(Looking at dromedary's past build results, it's evident that this
problem also breaks pg_strtouint64() on 32-bit platforms; but we
evidently have no regression tests that exercise that function with
values above 32 bits.)

To fix, supply declarations for these functions when the platform
provides the functions but not the declarations, using the same type
of mechanism as we use for some other similar cases.

Discussion: https://postgr.es/m/151935568942.1461.14623890240535309745@wrigleys.postgresql.org

5 files changed, 48 insertions, 0 deletions

diff --git a/configure b/configure
index 0aafd9c8c06..6acbc6e900d 100755
--- a/configure
+++ b/configure
@@ -15734,6 +15734,28 @@ _ACEOF
 fi
 done
 
+# strto[u]ll may exist but not be declared
+ac_fn_c_check_decl "$LINENO" "strtoll" "ac_cv_have_decl_strtoll" "$ac_includes_default"
+if test "x$ac_cv_have_decl_strtoll" = xyes; then :
+  ac_have_decl=1
+else
+  ac_have_decl=0
+fi
+
+cat >>confdefs.h <<_ACEOF
+#define HAVE_DECL_STRTOLL $ac_have_decl
+_ACEOF
+ac_fn_c_check_decl "$LINENO" "strtoull" "ac_cv_have_decl_strtoull" "$ac_includes_default"
+if test "x$ac_cv_have_decl_strtoull" = xyes; then :
+  ac_have_decl=1
+else
+  ac_have_decl=0
+fi
+
+cat >>confdefs.h <<_ACEOF
+#define HAVE_DECL_STRTOULL $ac_have_decl
+_ACEOF
+
 
 if test "$with_icu" = yes; then
   ac_save_CPPFLAGS=$CPPFLAGS
diff --git a/configure.in b/configure.in
index c3841d5b07f..8ea521a2177 100644
--- a/configure.in
+++ b/configure.in
@@ -1751,6 +1751,8 @@ fi
 
 AC_CHECK_FUNCS([strtoll strtoq], [break])
 AC_CHECK_FUNCS([strtoull strtouq], [break])
+# strto[u]ll may exist but not be declared
+AC_CHECK_DECLS([strtoll, strtoull])
 
 if test "$with_icu" = yes; then
   ac_save_CPPFLAGS=$CPPFLAGS
diff --git a/src/include/c.h b/src/include/c.h
index 95e9aeded9d..d88db02c6de 100644
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -1096,6 +1096,14 @@ extern int	snprintf(char *str, size_t count, const char *fmt,...) pg_attribute_p
 extern int	vsnprintf(char *str, size_t count, const char *fmt, va_list args);
 #endif
 
+#if defined(HAVE_LONG_LONG_INT) && defined(HAVE_STRTOLL) && !HAVE_DECL_STRTOLL
+extern long long strtoll(const char *str, char **endptr, int base);
+#endif
+
+#if defined(HAVE_LONG_LONG_INT) && defined(HAVE_STRTOULL) && !HAVE_DECL_STRTOULL
+extern unsigned long long strtoull(const char *str, char **endptr, int base);
+#endif
+
 #if !defined(HAVE_MEMMOVE) && !defined(memmove)
 #define memmove(d, s, c)		bcopy(s, d, c)
 #endif
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index 9411f485121..e2ffaa28a0a 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -170,6 +170,14 @@
    don't. */
 #undef HAVE_DECL_STRNLEN
 
+/* Define to 1 if you have the declaration of `strtoll', and to 0 if you
+   don't. */
+#undef HAVE_DECL_STRTOLL
+
+/* Define to 1 if you have the declaration of `strtoull', and to 0 if you
+   don't. */
+#undef HAVE_DECL_STRTOULL
+
 /* Define to 1 if you have the declaration of `sys_siglist', and to 0 if you
    don't. */
 #undef HAVE_DECL_SYS_SIGLIST
diff --git a/src/include/pg_config.h.win32 b/src/include/pg_config.h.win32
index a62bcac64e2..1a63dc4dc9a 100644
--- a/src/include/pg_config.h.win32
+++ b/src/include/pg_config.h.win32
@@ -122,6 +122,14 @@
    don't. */
 #define HAVE_DECL_STRNLEN 1
 
+/* Define to 1 if you have the declaration of `strtoll', and to 0 if you
+   don't. */
+#define HAVE_DECL_STRTOLL 1
+
+/* Define to 1 if you have the declaration of `strtoull', and to 0 if you
+   don't. */
+#define HAVE_DECL_STRTOULL 1
+
 /* Define to 1 if you have the declaration of `vsnprintf', and to 0 if you
    don't. */
 #define HAVE_DECL_VSNPRINTF 1