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Distinguish printf-like functions that support %m from those that don't.

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The elog/ereport family of functions certainly support the %m format spec,
because they implement it "by hand".  But elsewhere we have printf wrappers
that might or might not allow it depending on whether the platform's printf
does.  (Most non-glibc versions don't, and notably, src/port/snprintf.c
doesn't.)  Hence, rather than using the gnu_printf format archetype
interchangeably for all these functions, use it only for elog/ereport.
This will allow us to get compiler warnings for mistakes like the ones
fixed in commit a13b47a59, at least on platforms where printf doesn't
take %m and gcc is correctly configured to know it.  (Unfortunately,
that won't happen on Linux, nor on macOS according to my testing.
It remains to be seen what the buildfarm's gcc-on-Windows animals will
think of this, but we may well have to rely on less-popular platforms
to warn us about unportable code of this kind.)

Discussion: https://postgr.es/m/2975.1526862605@sss.pgh.pa.us
This commit is contained in:
Tom Lane 2018-08-11 11:11:05 -04:00
parent 5c047fd709
commit 3a60c8ff89
5 changed files with 32 additions and 28 deletions
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14
config/c-compiler.m4
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@ -19,12 +19,12 @@ fi])# PGAC_C_SIGNED
# PGAC_C_PRINTF_ARCHETYPE # PGAC_C_PRINTF_ARCHETYPE
# ----------------------- # -----------------------
# Set the format archetype used by gcc to check printf type functions. We # Set the format archetype used by gcc to check elog/ereport functions.
# prefer "gnu_printf", which includes what glibc uses, such as %m for error # This should accept %m, whether or not the platform's printf does.
# strings and %lld for 64 bit long longs. GCC 4.4 introduced it. It makes a # We use "gnu_printf" if possible, which does that, although in some cases
# dramatic difference on Windows. # it might do more than we could wish.
AC_DEFUN([PGAC_PRINTF_ARCHETYPE], AC_DEFUN([PGAC_PRINTF_ARCHETYPE],
[AC_CACHE_CHECK([for printf format archetype], pgac_cv_printf_archetype, [AC_CACHE_CHECK([for printf format archetype for %m], pgac_cv_printf_archetype,
[ac_save_c_werror_flag=$ac_c_werror_flag [ac_save_c_werror_flag=$ac_c_werror_flag
ac_c_werror_flag=yes ac_c_werror_flag=yes
AC_COMPILE_IFELSE([AC_LANG_PROGRAM( AC_COMPILE_IFELSE([AC_LANG_PROGRAM(
@ -34,8 +34,8 @@ __attribute__((format(gnu_printf, 2, 3)));], [])],
[pgac_cv_printf_archetype=gnu_printf], [pgac_cv_printf_archetype=gnu_printf],
[pgac_cv_printf_archetype=printf]) [pgac_cv_printf_archetype=printf])
ac_c_werror_flag=$ac_save_c_werror_flag]) ac_c_werror_flag=$ac_save_c_werror_flag])
AC_DEFINE_UNQUOTED([PG_PRINTF_ATTRIBUTE], [$pgac_cv_printf_archetype], AC_DEFINE_UNQUOTED([PG_PRINTF_ATTRIBUTE_M], [$pgac_cv_printf_archetype],
[Define to gnu_printf if compiler supports it, else printf.]) [Define as a format archetype that accepts %m, if available, else printf.])
])# PGAC_PRINTF_ARCHETYPE ])# PGAC_PRINTF_ARCHETYPE

6
configure vendored
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@ -13362,8 +13362,8 @@ _ACEOF
;; ;;
esac esac
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for printf format archetype" >&5 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for printf format archetype for %m" >&5
$as_echo_n "checking for printf format archetype... " >&6; } $as_echo_n "checking for printf format archetype for %m... " >&6; }
if ${pgac_cv_printf_archetype+:} false; then : if ${pgac_cv_printf_archetype+:} false; then :
$as_echo_n "(cached) " >&6 $as_echo_n "(cached) " >&6
else else
@ -13394,7 +13394,7 @@ fi
$as_echo "$pgac_cv_printf_archetype" >&6; } $as_echo "$pgac_cv_printf_archetype" >&6; }
cat >>confdefs.h <<_ACEOF cat >>confdefs.h <<_ACEOF
#define PG_PRINTF_ATTRIBUTE $pgac_cv_printf_archetype #define PG_PRINTF_ATTRIBUTE_M $pgac_cv_printf_archetype
_ACEOF _ACEOF

6
src/include/c.h
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@ -126,10 +126,14 @@
/* GCC and XLC support format attributes */ /* GCC and XLC support format attributes */
#if defined(__GNUC__) || defined(__IBMC__) #if defined(__GNUC__) || defined(__IBMC__)
#define pg_attribute_format_arg(a) __attribute__((format_arg(a))) #define pg_attribute_format_arg(a) __attribute__((format_arg(a)))
#define pg_attribute_printf(f,a) __attribute__((format(PG_PRINTF_ATTRIBUTE, f, 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 #else
#define pg_attribute_format_arg(a) #define pg_attribute_format_arg(a)
#define pg_attribute_printf(f,a) #define pg_attribute_printf(f,a)
#define pg_attribute_printf_m(f,a)
#endif #endif
/* GCC, Sunpro and XLC support aligned, packed and noreturn */ /* GCC, Sunpro and XLC support aligned, packed and noreturn */

4
src/include/pg_config.h.in
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@ -809,8 +809,8 @@
/* PostgreSQL major version as a string */ /* PostgreSQL major version as a string */
#undef PG_MAJORVERSION #undef PG_MAJORVERSION
/* Define to gnu_printf if compiler supports it, else printf. */ /* Define as a format archetype that accepts %m, if available, else printf. */
#undef PG_PRINTF_ATTRIBUTE #undef PG_PRINTF_ATTRIBUTE_M
/* PostgreSQL version as a string */ /* PostgreSQL version as a string */
#undef PG_VERSION #undef PG_VERSION

30
src/include/utils/elog.h
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@ -133,25 +133,25 @@ extern int errcode(int sqlerrcode);
extern int errcode_for_file_access(void); extern int errcode_for_file_access(void);
extern int errcode_for_socket_access(void); extern int errcode_for_socket_access(void);
extern int errmsg(const char *fmt,...) pg_attribute_printf(1, 2); extern int errmsg(const char *fmt,...) pg_attribute_printf_m(1, 2);
extern int errmsg_internal(const char *fmt,...) pg_attribute_printf(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, 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); unsigned long n,...) pg_attribute_printf_m(1, 4) pg_attribute_printf_m(2, 4);
extern int errdetail(const char *fmt,...) pg_attribute_printf(1, 2); extern int errdetail(const char *fmt,...) pg_attribute_printf_m(1, 2);
extern int errdetail_internal(const char *fmt,...) pg_attribute_printf(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(1, 2); extern int errdetail_log(const char *fmt,...) pg_attribute_printf_m(1, 2);
extern int errdetail_log_plural(const char *fmt_singular, extern int errdetail_log_plural(const char *fmt_singular,
const char *fmt_plural, const char *fmt_plural,
unsigned long n,...) pg_attribute_printf(1, 4) pg_attribute_printf(2, 4); 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, 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); unsigned long n,...) pg_attribute_printf_m(1, 4) pg_attribute_printf_m(2, 4);
extern int errhint(const char *fmt,...) pg_attribute_printf(1, 2); extern int errhint(const char *fmt,...) pg_attribute_printf_m(1, 2);
/* /*
* errcontext() is typically called in error context callback functions, not * errcontext() is typically called in error context callback functions, not
@ -165,7 +165,7 @@ extern int errhint(const char *fmt,...) pg_attribute_printf(1, 2);
extern int set_errcontext_domain(const char *domain); extern int set_errcontext_domain(const char *domain);
extern int errcontext_msg(const char *fmt,...) pg_attribute_printf(1, 2); extern int errcontext_msg(const char *fmt,...) pg_attribute_printf_m(1, 2);
extern int errhidestmt(bool hide_stmt); extern int errhidestmt(bool hide_stmt);
extern int errhidecontext(bool hide_ctx); extern int errhidecontext(bool hide_ctx);
@ -222,13 +222,13 @@ extern int getinternalerrposition(void);
#endif /* HAVE__VA_ARGS */ #endif /* HAVE__VA_ARGS */
extern void elog_start(const char *filename, int lineno, const char *funcname); 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); extern void elog_finish(int elevel, const char *fmt,...) pg_attribute_printf_m(2, 3);
/* Support for constructing error strings separately from ereport() calls */ /* Support for constructing error strings separately from ereport() calls */
extern void pre_format_elog_string(int errnumber, const char *domain); extern void pre_format_elog_string(int errnumber, const char *domain);
extern char *format_elog_string(const char *fmt,...) pg_attribute_printf(1, 2); extern char *format_elog_string(const char *fmt,...) pg_attribute_printf_m(1, 2);
/* Support for attaching context information to error reports */ /* Support for attaching context information to error reports */
@ -407,9 +407,9 @@ extern void set_syslog_parameters(const char *ident, int facility);
#endif #endif
/* /*
* Write errors to stderr (or by equal means when stderr is * Write errors to stderr (or by comparable means when stderr is not
* not available). Used before ereport/elog can be used * available). Used before ereport/elog can be used safely (memory context,
* safely (memory context, GUC load etc) * GUC load etc). Note that this does *not* accept "%m".
*/ */
extern void write_stderr(const char *fmt,...) pg_attribute_printf(1, 2); extern void write_stderr(const char *fmt,...) pg_attribute_printf(1, 2);