>From 94a3f93f4c8a381358a4dc52a43ec60a8f3e33f6 Mon Sep 17 00:00:00 2001 From: Andres Freund Date: Fri, 11 Jan 2013 16:58:17 +0100 Subject: [PATCH] Mark elog() as not returning if the capabilities of the C compiler allow it To do that: * Add a configure check for __VA_ARGS__ support * Provide pg_unreachable() macro which expands to__builtin_unreachable() if the compiler supports it, abort() otherwise Marking it as such improves code generation and reduces executable size. --- config/c-compiler.m4 | 41 +++++++++++++++++++++++++++++++++++++++++ configure.in | 2 ++ src/include/c.h | 10 ++++++++++ src/include/utils/elog.h | 18 +++++++++++++++--- 4 files changed, 68 insertions(+), 3 deletions(-) diff --git a/config/c-compiler.m4 b/config/c-compiler.m4 index 7cbb8ec..f3efe72 100644 --- a/config/c-compiler.m4 +++ b/config/c-compiler.m4 @@ -161,6 +161,47 @@ fi])# PGAC_C_TYPES_COMPATIBLE +# PGAC_C_VA_ARGS +# ----------------------- +# Check if the C compiler understands C99 style variadic macros and define +# HAVE__VA_ARGS if so. +AC_DEFUN([PGAC_C_VA_ARGS], +[AC_CACHE_CHECK(for __VA_ARGS__, pgac_cv__va_args, +[AC_TRY_COMPILE([#include ], +[#define debug(...) fprintf(stderr, __VA_ARGS__) +debug("%s", "blarg"); +], +[pgac_cv__va_args=yes], +[pgac_cv__va_args=no])]) +if test x"$pgac_cv__va_args" = xyes ; then +AC_DEFINE(HAVE__VA_ARGS, 1, + [Define to 1 if your compiler understands C99 __VA_ARGS__ in macros.]) +fi])# PGAC_C_VA_ARGS + + + +# PGAC_C_UNREACHABLE +# ----------------------- + +# Check if the C compiler understands __builtin_unreachable() and define +# HAVE__BUILTIN_UNREACHABLE if so. +# +# NB: Don't get the idea of putting a for(;;); or such before the +# __builtin_unreachable() in that case some compilers remove it before linking +# and only a warning instead of an error will be produced. +AC_DEFUN([PGAC_C_UNREACHABLE], +[AC_CACHE_CHECK(for __builtin_unreachable, pgac_cv__builtin_unreachable, +[AC_TRY_LINK([], +[__builtin_unreachable();], +[pgac_cv__builtin_unreachable=yes], +[pgac_cv__builtin_unreachable=no])]) +if test x"$pgac_cv__builtin_unreachable" = xyes ; then +AC_DEFINE(HAVE__BUILTIN_UNREACHABLE, 1, + [Define to 1 if your compiler understands __builtin_unreachable.]) +fi])# PGAC_C_UNREACHABLE + + + # PGAC_PROG_CC_CFLAGS_OPT # ----------------------- # Given a string, check if the compiler supports the string as a diff --git a/configure.in b/configure.in index e2682f3..13ac2ab 100644 --- a/configure.in +++ b/configure.in @@ -1106,6 +1106,8 @@ AC_C_VOLATILE PGAC_C_FUNCNAME_SUPPORT PGAC_C_STATIC_ASSERT PGAC_C_TYPES_COMPATIBLE +PGAC_C_VA_ARGS +PGAC_C_UNREACHABLE PGAC_STRUCT_TIMEZONE PGAC_UNION_SEMUN PGAC_STRUCT_SOCKADDR_UN diff --git a/src/include/c.h b/src/include/c.h index c30df8b..77c3319 100644 --- a/src/include/c.h +++ b/src/include/c.h @@ -831,6 +831,16 @@ typedef NameData *Name; #define STATIC_IF_INLINE #endif /* PG_USE_INLINE */ +/* + * Cross Platform support to mark locations as unreachable to avoid warnings + * and to aid code generation. + */ +#ifdef HAVE__BUILTIN_UNREACHABLE +#define pg_unreachable() __builtin_unreachable() +#else +#define pg_unreachable() abort() +#endif + /* ---------------------------------------------------------------- * Section 7: random stuff * ---------------------------------------------------------------- diff --git a/src/include/utils/elog.h b/src/include/utils/elog.h index cbbda04..d6e1054 100644 --- a/src/include/utils/elog.h +++ b/src/include/utils/elog.h @@ -109,7 +109,7 @@ #define ereport_domain(elevel, domain, rest) \ (errstart(elevel, __FILE__, __LINE__, PG_FUNCNAME_MACRO, domain) ? \ (errfinish rest) : (void) 0), \ - ((elevel) >= ERROR ? abort() : (void) 0) + ((elevel) >= ERROR ? pg_unreachable() : (void) 0) #define ereport(elevel, rest) \ ereport_domain(elevel, TEXTDOMAIN, rest) @@ -210,10 +210,22 @@ extern int getinternalerrposition(void); /*---------- * Old-style error reporting API: to be used in this way: * elog(ERROR, "portal \"%s\" not found", stmt->portalname); + * + * If we have support for variadic macros available we can signal that elog + * won't return with an elevel >= ERROR which can lead to better code being + * generated. *---------- */ -#define elog elog_start(__FILE__, __LINE__, PG_FUNCNAME_MACRO), elog_finish - +#ifdef HAVE__VA_ARGS +#define elog(elevel, ...) \ + elog_start(__FILE__, __LINE__, PG_FUNCNAME_MACRO), \ + elog_finish(elevel, __VA_ARGS__), \ + ((elevel) >= ERROR ? pg_unreachable() : (void) 0) +#else +#define elog \ + elog_start(__FILE__, __LINE__, PG_FUNCNAME_MACRO), \ + elog_finish +#endif extern void elog_start(const char *filename, int lineno, const char *funcname); extern void elog_finish(int elevel, const char *fmt,...) -- 1.7.12.289.g0ce9864.dirty