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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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6
src/include/c.h
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@@ -126,10 +126,14 @@
/* 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)))
/* 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 */

4
src/include/pg_config.h.in
View File

@@ -809,8 +809,8 @@
/* PostgreSQL major version as a string */
#undef PG_MAJORVERSION
/* Define to gnu_printf if compiler supports it, else printf. */
#undef PG_PRINTF_ATTRIBUTE
/* 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

30
src/include/utils/elog.h
View File

@@ -133,25 +133,25 @@ extern int errcode(int sqlerrcode);
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(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(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_internal(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_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,
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,
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
@@ -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 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 errhidecontext(bool hide_ctx);
@@ -222,13 +222,13 @@ extern int getinternalerrposition(void);
#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);
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(1, 2);
extern char *format_elog_string(const char *fmt,...) pg_attribute_printf_m(1, 2);
/* Support for attaching context information to error reports */
@@ -407,9 +407,9 @@ extern void set_syslog_parameters(const char *ident, int facility);
#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)
* 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);