When in C11 mode, MSVC supports the standard "restrict" keyword, so we
don't need the workaround with using "pg_restrict" instead anymore.
(Just for clarification, restrict is a C99 feature, but MSVC only
accepts it properly in C11 mode.) So I'm proposing to remove that
workaround here, so that code can use the standard restrict keyword
without having to worry about the alternative spelling.
However, "restrict" does not exist in C++, but all supported compilers
support the spelling "__restrict" in C++. Therefore, I'm leaving in
place the Autoconf test and the equivalent Meson business, to maintain
the status quo with respect to C++. I'm updating the comments about
that a bit. (In a C++-free world, we could have plausibly removed the
Autoconf test altogether.)
While making the required adjustments, I found a few pieces of code that
use restrict (previously pg_restrict) in what appears to me to be
nonsensical ways, like
memcpy((char *pg_restrict) (buf->data + buf->len), &ni, sizeof(uint16));
The restrict qualifier is not meaningful in casts, so I'm confused about
why it is used here. I did not find any indications either in the old
discussions leading up to this change or on the wider web that there are
any other interpretations or compiler extensions or perhaps a C++ angle
that would make this meaningful. Also, the generated code appears to be
the same if I remove this. So I'm proposing to remove redundant casts
like this.
From 708a9e51e7a73df72c1632ab2dab0c450d925954 Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <[email protected]>
Date: Wed, 15 Oct 2025 10:14:06 +0200
Subject: [PATCH 1/2] Remove meaninglist restrict qualifiers
The use of the restrict qualifier in casts is meaningless, so remove
it.
---
src/include/libpq/pqformat.h | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/src/include/libpq/pqformat.h b/src/include/libpq/pqformat.h
index 9a1534be521..55442caf0e4 100644
--- a/src/include/libpq/pqformat.h
+++ b/src/include/libpq/pqformat.h
@@ -48,7 +48,7 @@ pq_writeint8(StringInfoData *pg_restrict buf, uint8 i)
uint8 ni = i;
Assert(buf->len + (int) sizeof(uint8) <= buf->maxlen);
- memcpy((char *pg_restrict) (buf->data + buf->len), &ni, sizeof(uint8));
+ memcpy(buf->data + buf->len, &ni, sizeof(uint8));
buf->len += sizeof(uint8);
}
@@ -62,7 +62,7 @@ pq_writeint16(StringInfoData *pg_restrict buf, uint16 i)
uint16 ni = pg_hton16(i);
Assert(buf->len + (int) sizeof(uint16) <= buf->maxlen);
- memcpy((char *pg_restrict) (buf->data + buf->len), &ni, sizeof(uint16));
+ memcpy(buf->data + buf->len, &ni, sizeof(uint16));
buf->len += sizeof(uint16);
}
@@ -76,7 +76,7 @@ pq_writeint32(StringInfoData *pg_restrict buf, uint32 i)
uint32 ni = pg_hton32(i);
Assert(buf->len + (int) sizeof(uint32) <= buf->maxlen);
- memcpy((char *pg_restrict) (buf->data + buf->len), &ni, sizeof(uint32));
+ memcpy(buf->data + buf->len, &ni, sizeof(uint32));
buf->len += sizeof(uint32);
}
@@ -90,7 +90,7 @@ pq_writeint64(StringInfoData *pg_restrict buf, uint64 i)
uint64 ni = pg_hton64(i);
Assert(buf->len + (int) sizeof(uint64) <= buf->maxlen);
- memcpy((char *pg_restrict) (buf->data + buf->len), &ni, sizeof(uint64));
+ memcpy(buf->data + buf->len, &ni, sizeof(uint64));
buf->len += sizeof(uint64);
}
@@ -116,7 +116,7 @@ pq_writestring(StringInfoData *pg_restrict buf, const char
*pg_restrict str)
Assert(buf->len + slen + 1 <= buf->maxlen);
- memcpy(((char *pg_restrict) buf->data + buf->len), p, slen + 1);
+ memcpy(buf->data + buf->len, p, slen + 1);
buf->len += slen + 1;
if (p != str)
--
2.51.0
From 0cc4796822a97d265927fd260ace56c24ca95ac9 Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <[email protected]>
Date: Wed, 15 Oct 2025 13:35:55 +0200
Subject: [PATCH 2/2] Replace pg_restrict by standard restrict
MSVC in C11 mode supports the standard restrict qualifier, so we don't
need the workaround naming pg_restrict anymore.
Even though restrict is in C99 and should be supported by all
supported compilers, we keep the configure test and the hardcoded
redirection to __restrict, because that will also work in C++ in all
supported compilers. (restrict is not part of the C++ standard.)
---
configure | 18 ++++--------------
configure.ac | 16 ++++------------
meson.build | 13 ++++++-------
src/bin/pg_verifybackup/pg_verifybackup.c | 4 ++--
src/bin/pg_verifybackup/pg_verifybackup.h | 4 ++--
src/common/logging.c | 4 ++--
src/common/string.c | 2 +-
src/include/common/logging.h | 4 ++--
src/include/common/string.h | 2 +-
src/include/libpq/pqformat.h | 12 ++++++------
src/include/pg_config.h.in | 4 ----
11 files changed, 30 insertions(+), 53 deletions(-)
diff --git a/configure b/configure
index 22cd866147b..7ce52173dd8 100755
--- a/configure
+++ b/configure
@@ -14999,10 +14999,10 @@ _ACEOF
fi
-# MSVC doesn't cope well with defining restrict to __restrict, the
-# spelling it understands, because it conflicts with
-# __declspec(restrict). Therefore we define pg_restrict to the
-# appropriate definition, which presumably won't conflict.
+# Even though restrict is in C99 and should be supported by all
+# supported compilers, but this macro is useful because it will prefer
+# a spelling that also works in C++ (often __restrict). (restrict is
+# not part of the C++ standard.)
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for C/C++ restrict keyword"
>&5
$as_echo_n "checking for C/C++ restrict keyword... " >&6; }
if ${ac_cv_c_restrict+:} false; then :
@@ -15049,16 +15049,6 @@ _ACEOF
;;
esac
-if test "$ac_cv_c_restrict" = "no"; then
- pg_restrict=""
-else
- pg_restrict="$ac_cv_c_restrict"
-fi
-
-cat >>confdefs.h <<_ACEOF
-#define pg_restrict $pg_restrict
-_ACEOF
-
ac_fn_c_check_type "$LINENO" "struct option" "ac_cv_type_struct_option"
"#ifdef HAVE_GETOPT_H
#include <getopt.h>
diff --git a/configure.ac b/configure.ac
index e44943aa6fe..19c93d0b391 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1685,19 +1685,11 @@ PGAC_UNION_SEMUN
AC_CHECK_TYPES(socklen_t, [], [], [#include <sys/socket.h>])
PGAC_STRUCT_SOCKADDR_SA_LEN
-# MSVC doesn't cope well with defining restrict to __restrict, the
-# spelling it understands, because it conflicts with
-# __declspec(restrict). Therefore we define pg_restrict to the
-# appropriate definition, which presumably won't conflict.
+# Even though restrict is in C99 and should be supported by all
+# supported compilers, but this macro is useful because it will prefer
+# a spelling that also works in C++ (often __restrict). (restrict is
+# not part of the C++ standard.)
AC_C_RESTRICT
-if test "$ac_cv_c_restrict" = "no"; then
- pg_restrict=""
-else
- pg_restrict="$ac_cv_c_restrict"
-fi
-AC_DEFINE_UNQUOTED([pg_restrict], [$pg_restrict],
-[Define to keyword to use for C99 restrict support, or to nothing if not
-supported])
AC_CHECK_TYPES([struct option], [], [],
[#ifdef HAVE_GETOPT_H
diff --git a/meson.build b/meson.build
index 395416a6060..d2315701114 100644
--- a/meson.build
+++ b/meson.build
@@ -2803,13 +2803,12 @@ int main(void)
endforeach
-# MSVC doesn't cope well with defining restrict to __restrict, the spelling it
-# understands, because it conflicts with __declspec(restrict). Therefore we
-# define pg_restrict to the appropriate definition, which presumably won't
-# conflict.
-#
-# We assume C99 support, so we don't need to make this conditional.
-cdata.set('pg_restrict', '__restrict')
+# Even though restrict is in C99 and should be supported by all
+# supported compilers, but this indirection is useful because
+# __restrict also works in C++ in all supported compilers. (If not,
+# then we might have to write a real test.) (restrict is not part of
+# the C++ standard.)
+cdata.set('restrict', '__restrict')
# Most libraries are included only if they demonstrably provide a function we
diff --git a/src/bin/pg_verifybackup/pg_verifybackup.c
b/src/bin/pg_verifybackup/pg_verifybackup.c
index 5e6c13bb921..8d5befa947f 100644
--- a/src/bin/pg_verifybackup/pg_verifybackup.c
+++ b/src/bin/pg_verifybackup/pg_verifybackup.c
@@ -1228,7 +1228,7 @@ parse_required_wal(verifier_context *context, char
*pg_waldump_path,
* context says we should.
*/
void
-report_backup_error(verifier_context *context, const char *pg_restrict fmt,...)
+report_backup_error(verifier_context *context, const char *restrict fmt,...)
{
va_list ap;
@@ -1245,7 +1245,7 @@ report_backup_error(verifier_context *context, const char
*pg_restrict fmt,...)
* Report a fatal error and exit
*/
void
-report_fatal_error(const char *pg_restrict fmt,...)
+report_fatal_error(const char *restrict fmt,...)
{
va_list ap;
diff --git a/src/bin/pg_verifybackup/pg_verifybackup.h
b/src/bin/pg_verifybackup/pg_verifybackup.h
index 8cb6f9c53ad..3bdae62b822 100644
--- a/src/bin/pg_verifybackup/pg_verifybackup.h
+++ b/src/bin/pg_verifybackup/pg_verifybackup.h
@@ -96,9 +96,9 @@ typedef struct verifier_context
} verifier_context;
extern void report_backup_error(verifier_context *context,
- const char
*pg_restrict fmt,...)
+ const char
*restrict fmt,...)
pg_attribute_printf(2, 3);
-pg_noreturn extern void report_fatal_error(const char *pg_restrict fmt,...)
+pg_noreturn extern void report_fatal_error(const char *restrict fmt,...)
pg_attribute_printf(1, 2);
extern bool should_ignore_relpath(verifier_context *context,
const char
*relpath);
diff --git a/src/common/logging.c b/src/common/logging.c
index 125a172af80..7319a5b4e20 100644
--- a/src/common/logging.c
+++ b/src/common/logging.c
@@ -206,7 +206,7 @@ pg_logging_set_locus_callback(void (*cb) (const char
**filename, uint64 *lineno)
void
pg_log_generic(enum pg_log_level level, enum pg_log_part part,
- const char *pg_restrict fmt,...)
+ const char *restrict fmt,...)
{
va_list ap;
@@ -217,7 +217,7 @@ pg_log_generic(enum pg_log_level level, enum pg_log_part
part,
void
pg_log_generic_v(enum pg_log_level level, enum pg_log_part part,
- const char *pg_restrict fmt, va_list ap)
+ const char *restrict fmt, va_list ap)
{
int save_errno = errno;
const char *filename = NULL;
diff --git a/src/common/string.c b/src/common/string.c
index d8a3129c3ba..95c7c07d502 100644
--- a/src/common/string.c
+++ b/src/common/string.c
@@ -47,7 +47,7 @@ pg_str_endswith(const char *str, const char *end)
* strtoint --- just like strtol, but returns int not long
*/
int
-strtoint(const char *pg_restrict str, char **pg_restrict endptr, int base)
+strtoint(const char *restrict str, char **restrict endptr, int base)
{
long val;
diff --git a/src/include/common/logging.h b/src/include/common/logging.h
index 81529ee8f29..2e0333dc009 100644
--- a/src/include/common/logging.h
+++ b/src/include/common/logging.h
@@ -93,10 +93,10 @@ void pg_logging_set_pre_callback(void (*cb)
(void));
void pg_logging_set_locus_callback(void (*cb) (const char
**filename, uint64 *lineno));
void pg_log_generic(enum pg_log_level level, enum pg_log_part part,
- const char *pg_restrict
fmt,...)
+ const char *restrict fmt,...)
pg_attribute_printf(3, 4);
void pg_log_generic_v(enum pg_log_level level, enum pg_log_part part,
- const char
*pg_restrict fmt, va_list ap)
+ const char *restrict
fmt, va_list ap)
pg_attribute_printf(3, 0);
/*
diff --git a/src/include/common/string.h b/src/include/common/string.h
index 55ed8774364..32a97c24b22 100644
--- a/src/include/common/string.h
+++ b/src/include/common/string.h
@@ -25,7 +25,7 @@ typedef struct PromptInterruptContext
/* functions in src/common/string.c */
extern bool pg_str_endswith(const char *str, const char *end);
-extern int strtoint(const char *pg_restrict str, char **pg_restrict endptr,
+extern int strtoint(const char *restrict str, char **restrict endptr,
int base);
extern char *pg_clean_ascii(const char *str, int alloc_flags);
extern int pg_strip_crlf(char *str);
diff --git a/src/include/libpq/pqformat.h b/src/include/libpq/pqformat.h
index 55442caf0e4..127a74e299a 100644
--- a/src/include/libpq/pqformat.h
+++ b/src/include/libpq/pqformat.h
@@ -34,7 +34,7 @@ extern void pq_sendfloat8(StringInfo buf, float8 f);
* Append a [u]int8 to a StringInfo buffer, which already has enough space
* preallocated.
*
- * The use of pg_restrict allows the compiler to optimize the code based on
+ * The use of restrict allows the compiler to optimize the code based on
* the assumption that buf, buf->len, buf->data and *buf->data don't
* overlap. Without the annotation buf->len etc cannot be kept in a register
* over subsequent pq_writeintN calls.
@@ -43,7 +43,7 @@ extern void pq_sendfloat8(StringInfo buf, float8 f);
* overly picky and demanding a * before a restrict.
*/
static inline void
-pq_writeint8(StringInfoData *pg_restrict buf, uint8 i)
+pq_writeint8(StringInfoData *restrict buf, uint8 i)
{
uint8 ni = i;
@@ -57,7 +57,7 @@ pq_writeint8(StringInfoData *pg_restrict buf, uint8 i)
* preallocated.
*/
static inline void
-pq_writeint16(StringInfoData *pg_restrict buf, uint16 i)
+pq_writeint16(StringInfoData *restrict buf, uint16 i)
{
uint16 ni = pg_hton16(i);
@@ -71,7 +71,7 @@ pq_writeint16(StringInfoData *pg_restrict buf, uint16 i)
* preallocated.
*/
static inline void
-pq_writeint32(StringInfoData *pg_restrict buf, uint32 i)
+pq_writeint32(StringInfoData *restrict buf, uint32 i)
{
uint32 ni = pg_hton32(i);
@@ -85,7 +85,7 @@ pq_writeint32(StringInfoData *pg_restrict buf, uint32 i)
* preallocated.
*/
static inline void
-pq_writeint64(StringInfoData *pg_restrict buf, uint64 i)
+pq_writeint64(StringInfoData *restrict buf, uint64 i)
{
uint64 ni = pg_hton64(i);
@@ -105,7 +105,7 @@ pq_writeint64(StringInfoData *pg_restrict buf, uint64 i)
* sent to the frontend.
*/
static inline void
-pq_writestring(StringInfoData *pg_restrict buf, const char *pg_restrict str)
+pq_writestring(StringInfoData *restrict buf, const char *restrict str)
{
int slen = strlen(str);
char *p;
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index c4dc5d72bdb..08d7bfbee10 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -796,10 +796,6 @@
#undef inline
#endif
-/* Define to keyword to use for C99 restrict support, or to nothing if not
- supported */
-#undef pg_restrict
-
/* Define to the equivalent of the C99 'restrict' keyword, or to
nothing if this is not supported. Do not define if restrict is
supported directly. */
--
2.51.0
