From: Tom Lane <tgl@sss.pgh.pa.us>
To: Thomas Munro <thomas.munro@enterprisedb.com>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: Allowing printf("%m") only where it actually works
Date: Fri, 10 Aug 2018 16:05:11 -0400
Message-ID: <8770.1533931511@sss.pgh.pa.us> (raw)
In-Reply-To: <2685.1527520461@sss.pgh.pa.us>
References: <20180528150125.j2x3mp62ssbeg3h5@alvherre.pgsql>
<2685.1527520461@sss.pgh.pa.us>
In the hopes of getting the cfbot un-stuck (it's currently trying to
test a known-not-to-work patch), here are updated versions of the two
live patches we have in this thread.
0001 is the patch I originally proposed to adjust printf archetypes.
0002 is Thomas's patch to blow up on errno references in ereport/elog,
plus changes in src/common/exec.c to prevent that from blowing up.
(I went with the minimum-footprint way, for now; making exec.c's
error handling generally nicer seems like a task for another day.)
I think 0002 is probably pushable, really. The unresolved issue about
0001 is whether it will create a spate of warnings on Windows builds,
and if so what to do about it. We might learn something from the
cfbot about that, but I think the full buildfarm is going to be the
only really authoritative answer.
There's also the matter of providing similar safety for GetLastError
calls, but I think that deserves to be a separate patch ... and I don't
really want to take point on it since I lack a Windows machine.
regards, tom lane
Attachments:download all (2 files, .tar.gz)0001-get-compiler-warnings-for-misuse-of-percent-m-2.patch (text/x-diff, 9.0K) downloaddiff --git a/config/c-compiler.m4 b/config/c-compiler.m4index 9731a51..5e56ca5 100644
*** a/config/c-compiler.m4
--- b/config/c-compiler.m4
*************** fi])# PGAC_C_SIGNED
*** 19,28 ****
# PGAC_C_PRINTF_ARCHETYPE
# -----------------------
! # Set the format archetype used by gcc to check printf type functions. We
! # prefer "gnu_printf", which includes what glibc uses, such as %m for error
! # strings and %lld for 64 bit long longs. GCC 4.4 introduced it. It makes a
! # dramatic difference on Windows.
AC_DEFUN([PGAC_PRINTF_ARCHETYPE],
[AC_CACHE_CHECK([for printf format archetype], pgac_cv_printf_archetype,
[ac_save_c_werror_flag=$ac_c_werror_flag
--- 19,28 ----
# PGAC_C_PRINTF_ARCHETYPE
# -----------------------
! # Set the format archetype used by gcc to check elog/ereport functions.
! # This should accept %m, whether or not the platform's printf does.
! # We use "gnu_printf" if possible, which does that, although in some cases
! # it might do more than we could wish.
AC_DEFUN([PGAC_PRINTF_ARCHETYPE],
[AC_CACHE_CHECK([for printf format archetype], pgac_cv_printf_archetype,
[ac_save_c_werror_flag=$ac_c_werror_flag
*************** __attribute__((format(gnu_printf, 2, 3))
*** 34,41 ****
[pgac_cv_printf_archetype=gnu_printf],
[pgac_cv_printf_archetype=printf])
ac_c_werror_flag=$ac_save_c_werror_flag])
! AC_DEFINE_UNQUOTED([PG_PRINTF_ATTRIBUTE], [$pgac_cv_printf_archetype],
! [Define to gnu_printf if compiler supports it, else printf.])
])# PGAC_PRINTF_ARCHETYPE
--- 34,41 ----
[pgac_cv_printf_archetype=gnu_printf],
[pgac_cv_printf_archetype=printf])
ac_c_werror_flag=$ac_save_c_werror_flag])
! AC_DEFINE_UNQUOTED([PG_PRINTF_ATTRIBUTE_M], [$pgac_cv_printf_archetype],
! [Define as a format archetype that accepts %m, if available, else printf.])
])# PGAC_PRINTF_ARCHETYPE
diff --git a/configure b/configureindex 2665213..d4b4742 100755
*** a/configure
--- b/configure
*************** fi
*** 13394,13400 ****
$as_echo "$pgac_cv_printf_archetype" >&6; }
cat >>confdefs.h <<_ACEOF
! #define PG_PRINTF_ATTRIBUTE $pgac_cv_printf_archetype
_ACEOF
--- 13394,13400 ----
$as_echo "$pgac_cv_printf_archetype" >&6; }
cat >>confdefs.h <<_ACEOF
! #define PG_PRINTF_ATTRIBUTE_M $pgac_cv_printf_archetype
_ACEOF
diff --git a/src/include/c.h b/src/include/c.hindex 1e50103..0a4757e 100644
*** a/src/include/c.h
--- b/src/include/c.h
***************
*** 126,135 ****
/* GCC and XLC support format attributes */
#if defined(__GNUC__) || defined(__IBMC__)
#define pg_attribute_format_arg(a) __attribute__((format_arg(a)))
! #define pg_attribute_printf(f,a) __attribute__((format(PG_PRINTF_ATTRIBUTE, f, a)))
#else
#define pg_attribute_format_arg(a)
#define pg_attribute_printf(f,a)
#endif
/* GCC, Sunpro and XLC support aligned, packed and noreturn */
--- 126,139 ----
/* GCC and XLC support format attributes */
#if defined(__GNUC__) || defined(__IBMC__)
#define pg_attribute_format_arg(a) __attribute__((format_arg(a)))
! /* Use for functions wrapping stdio's printf, which often doesn't take %m: */
! #define pg_attribute_printf(f,a) __attribute__((format(printf, f, a)))
! /* Use for elog/ereport, which implement %m for themselves: */
! #define pg_attribute_printf_m(f,a) __attribute__((format(PG_PRINTF_ATTRIBUTE_M, f, a)))
#else
#define pg_attribute_format_arg(a)
#define pg_attribute_printf(f,a)
+ #define pg_attribute_printf_m(f,a)
#endif
/* GCC, Sunpro and XLC support aligned, packed and noreturn */
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.inindex b7e4696..05775a3 100644
*** a/src/include/pg_config.h.in
--- b/src/include/pg_config.h.in
***************
*** 809,816 ****
/* PostgreSQL major version as a string */
#undef PG_MAJORVERSION
! /* Define to gnu_printf if compiler supports it, else printf. */
! #undef PG_PRINTF_ATTRIBUTE
/* PostgreSQL version as a string */
#undef PG_VERSION
--- 809,816 ----
/* PostgreSQL major version as a string */
#undef PG_MAJORVERSION
! /* Define as a format archetype that accepts %m, if available, else printf. */
! #undef PG_PRINTF_ATTRIBUTE_M
/* PostgreSQL version as a string */
#undef PG_VERSION
diff --git a/src/include/utils/elog.h b/src/include/utils/elog.hindex 7a9ba7f..4f4091d 100644
*** a/src/include/utils/elog.h
--- b/src/include/utils/elog.h
*************** extern int errcode(int sqlerrcode);
*** 133,157 ****
extern int errcode_for_file_access(void);
extern int errcode_for_socket_access(void);
! extern int errmsg(const char *fmt,...) pg_attribute_printf(1, 2);
! extern int errmsg_internal(const char *fmt,...) pg_attribute_printf(1, 2);
extern int errmsg_plural(const char *fmt_singular, const char *fmt_plural,
! unsigned long n,...) pg_attribute_printf(1, 4) pg_attribute_printf(2, 4);
! extern int errdetail(const char *fmt,...) pg_attribute_printf(1, 2);
! extern int errdetail_internal(const char *fmt,...) pg_attribute_printf(1, 2);
! extern int errdetail_log(const char *fmt,...) pg_attribute_printf(1, 2);
extern int errdetail_log_plural(const char *fmt_singular,
const char *fmt_plural,
! unsigned long n,...) pg_attribute_printf(1, 4) pg_attribute_printf(2, 4);
extern int errdetail_plural(const char *fmt_singular, const char *fmt_plural,
! unsigned long n,...) pg_attribute_printf(1, 4) pg_attribute_printf(2, 4);
! extern int errhint(const char *fmt,...) pg_attribute_printf(1, 2);
/*
* errcontext() is typically called in error context callback functions, not
--- 133,157 ----
extern int errcode_for_file_access(void);
extern int errcode_for_socket_access(void);
! extern int errmsg(const char *fmt,...) pg_attribute_printf_m(1, 2);
! extern int errmsg_internal(const char *fmt,...) pg_attribute_printf_m(1, 2);
extern int errmsg_plural(const char *fmt_singular, const char *fmt_plural,
! unsigned long n,...) pg_attribute_printf_m(1, 4) pg_attribute_printf_m(2, 4);
! extern int errdetail(const char *fmt,...) pg_attribute_printf_m(1, 2);
! extern int errdetail_internal(const char *fmt,...) pg_attribute_printf_m(1, 2);
! extern int errdetail_log(const char *fmt,...) pg_attribute_printf_m(1, 2);
extern int errdetail_log_plural(const char *fmt_singular,
const char *fmt_plural,
! unsigned long n,...) pg_attribute_printf_m(1, 4) pg_attribute_printf_m(2, 4);
extern int errdetail_plural(const char *fmt_singular, const char *fmt_plural,
! unsigned long n,...) pg_attribute_printf_m(1, 4) pg_attribute_printf_m(2, 4);
! extern int errhint(const char *fmt,...) pg_attribute_printf_m(1, 2);
/*
* errcontext() is typically called in error context callback functions, not
*************** extern int errhint(const char *fmt,...)
*** 165,171 ****
extern int set_errcontext_domain(const char *domain);
! extern int errcontext_msg(const char *fmt,...) pg_attribute_printf(1, 2);
extern int errhidestmt(bool hide_stmt);
extern int errhidecontext(bool hide_ctx);
--- 165,171 ----
extern int set_errcontext_domain(const char *domain);
! extern int errcontext_msg(const char *fmt,...) pg_attribute_printf_m(1, 2);
extern int errhidestmt(bool hide_stmt);
extern int errhidecontext(bool hide_ctx);
*************** extern int getinternalerrposition(void);
*** 222,234 ****
#endif /* HAVE__VA_ARGS */
extern void elog_start(const char *filename, int lineno, const char *funcname);
! extern void elog_finish(int elevel, const char *fmt,...) pg_attribute_printf(2, 3);
/* Support for constructing error strings separately from ereport() calls */
extern void pre_format_elog_string(int errnumber, const char *domain);
! extern char *format_elog_string(const char *fmt,...) pg_attribute_printf(1, 2);
/* Support for attaching context information to error reports */
--- 222,234 ----
#endif /* HAVE__VA_ARGS */
extern void elog_start(const char *filename, int lineno, const char *funcname);
! extern void elog_finish(int elevel, const char *fmt,...) pg_attribute_printf_m(2, 3);
/* Support for constructing error strings separately from ereport() calls */
extern void pre_format_elog_string(int errnumber, const char *domain);
! extern char *format_elog_string(const char *fmt,...) pg_attribute_printf_m(1, 2);
/* Support for attaching context information to error reports */
*************** extern void set_syslog_parameters(const
*** 407,415 ****
#endif
/*
! * Write errors to stderr (or by equal means when stderr is
! * not available). Used before ereport/elog can be used
! * safely (memory context, GUC load etc)
*/
extern void write_stderr(const char *fmt,...) pg_attribute_printf(1, 2);
--- 407,415 ----
#endif
/*
! * Write errors to stderr (or by comparable means when stderr is not
! * available). Used before ereport/elog can be used safely (memory context,
! * GUC load etc). Note that this does *not* accept "%m".
*/
extern void write_stderr(const char *fmt,...) pg_attribute_printf(1, 2);
=
0002-prevent-errno-in-ereport-3.patch (text/x-diff, 4.2K) downloaddiff --git a/src/common/exec.c b/src/common/exec.cindex 4df16cd..c207c02 100644--- a/src/common/exec.c+++ b/src/common/exec.c@@ -124,8 +124,10 @@ find_my_exec(const char *argv0, char *retpath)
if (!getcwd(cwd, MAXPGPATH))
{
+ int save_errno = errno;+
log_error(_("could not identify current directory: %s"),
- strerror(errno));+ strerror(save_errno));
return -1;
}
@@ -238,8 +240,10 @@ resolve_symlinks(char *path)
*/
if (!getcwd(orig_wd, MAXPGPATH))
{
+ int save_errno = errno;+
log_error(_("could not identify current directory: %s"),
- strerror(errno));+ strerror(save_errno));
return -1;
}
@@ -254,7 +258,10 @@ resolve_symlinks(char *path)
*lsep = '\0';
if (chdir(path) == -1)
{
- log_error4(_("could not change directory to \"%s\": %s"), path, strerror(errno));+ int save_errno = errno;++ log_error4(_("could not change directory to \"%s\": %s"),+ path, strerror(save_errno));
return -1;
}
fname = lsep + 1;
@@ -281,8 +288,10 @@ resolve_symlinks(char *path)
if (!getcwd(path, MAXPGPATH))
{
+ int save_errno = errno;+
log_error(_("could not identify current directory: %s"),
- strerror(errno));+ strerror(save_errno));
return -1;
}
join_path_components(path, path, link_buf);
@@ -290,7 +299,10 @@ resolve_symlinks(char *path)
if (chdir(orig_wd) == -1)
{
- log_error4(_("could not change directory to \"%s\": %s"), orig_wd, strerror(errno));+ int save_errno = errno;++ log_error4(_("could not change directory to \"%s\": %s"),+ orig_wd, strerror(save_errno));
return -1;
}
#endif /* HAVE_READLINK */
@@ -520,7 +532,10 @@ pclose_check(FILE *stream)
if (exitstatus == -1)
{
/* pclose() itself failed, and hopefully set errno */
- log_error(_("pclose failed: %s"), strerror(errno));+ int save_errno = errno;++ log_error(_("pclose failed: %s"),+ strerror(save_errno));
}
else
{
diff --git a/src/include/utils/elog.h b/src/include/utils/elog.hindex 7a9ba7f..4350b12 100644--- a/src/include/utils/elog.h+++ b/src/include/utils/elog.h@@ -70,6 +70,23 @@
/* SQLSTATE codes for errors are defined in a separate file */
#include "utils/errcodes.h"
+/*+ * Provide a way to prevent "errno" from being accidentally used inside an+ * elog() or ereport() invocation. Since we know that some operating systems+ * define errno as something involving a function call, we'll put a local+ * variable of the same name as that function in the local scope to force a+ * compile error. On platforms that don't define errno in that way, nothing+ * happens, so we get no warning ... but we can live with that as long as it+ * happens on some popular platforms.+ */+#if defined(errno) && defined(__linux__)+#define pg_prevent_errno_in_scope() int __errno_location pg_attribute_unused()+#elif defined(errno) && (defined(__darwin__) || defined(__freebsd__))+#define pg_prevent_errno_in_scope() int __error pg_attribute_unused()+#else+#define pg_prevent_errno_in_scope()+#endif+
/*----------
* New-style error reporting API: to be used in this way:
@@ -103,6 +120,7 @@
#ifdef HAVE__BUILTIN_CONSTANT_P
#define ereport_domain(elevel, domain, rest) \
do { \
+ pg_prevent_errno_in_scope(); \
if (errstart(elevel, __FILE__, __LINE__, PG_FUNCNAME_MACRO, domain)) \
errfinish rest; \
if (__builtin_constant_p(elevel) && (elevel) >= ERROR) \
@@ -112,6 +130,7 @@
#define ereport_domain(elevel, domain, rest) \
do { \
const int elevel_ = (elevel); \
+ pg_prevent_errno_in_scope(); \
if (errstart(elevel_, __FILE__, __LINE__, PG_FUNCNAME_MACRO, domain)) \
errfinish rest; \
if (elevel_ >= ERROR) \
@@ -198,6 +217,7 @@ extern int getinternalerrposition(void);
#ifdef HAVE__BUILTIN_CONSTANT_P
#define elog(elevel, ...) \
do { \
+ pg_prevent_errno_in_scope(); \
elog_start(__FILE__, __LINE__, PG_FUNCNAME_MACRO); \
elog_finish(elevel, __VA_ARGS__); \
if (__builtin_constant_p(elevel) && (elevel) >= ERROR) \
@@ -206,6 +226,7 @@ extern int getinternalerrposition(void);
#else /* !HAVE__BUILTIN_CONSTANT_P */
#define elog(elevel, ...) \
do { \
+ pg_prevent_errno_in_scope(); \
elog_start(__FILE__, __LINE__, PG_FUNCNAME_MACRO); \
{ \
const int elevel_ = (elevel); \
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To: pgsql-hackers@postgresql.org
Cc: tgl@sss.pgh.pa.us, thomas.munro@enterprisedb.com, alvherre@2ndquadrant.com, pgsql-hackers@lists.postgresql.org
Subject: Re: Allowing printf("%m") only where it actually works
In-Reply-To: <8770.1533931511@sss.pgh.pa.us>
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