From 61f76a3612db199a9eb9090c2605d8fc35ffc41c Mon Sep 17 00:00:00 2001 From: Kirill Smelkov Date: Thu, 27 Mar 2014 18:22:50 +0400 Subject: [PATCH] Portable alloca for Git In the next patch we'll have to use alloca() for performance reasons, but since alloca is non-standardized and is not portable, let's have a trick with compatibility wrappers: 1. at configure time, determine, do we have working alloca() through alloca.h, and define #define HAVE_ALLOCA_H if yes. 2. in code #ifdef HAVE_ALLOCA_H # include # define xalloca(size) (alloca(size)) # define xalloca_free(p) do {} while(0) #else # define xalloca(size) (xmalloc(size)) # define xalloca_free(p) (free(p)) #endif and use it like func() { p = xalloca(size); ... xalloca_free(p); } This way, for systems, where alloca is available, we'll have optimal on-stack allocations with fast executions. On the other hand, on systems, where alloca is not available, this gracefully fallbacks to xmalloc/free. Both autoconf and config.mak.uname configurations were updated. For autoconf, we are not bothering considering cases, when no alloca.h is available, but alloca() works some other way - its simply alloca.h is available and works or not, everything else is deep legacy. For config.mak.uname, I've tried to make my almost-sure guess for where alloca() is available, but since I only have access to Linux it is the only change I can be sure about myself, with relevant to other changed systems people Cc'ed. NOTE SunOS and Windows had explicit -DHAVE_ALLOCA_H in their configurations. I've changed that to now-common HAVE_ALLOCA_H=YesPlease which should be correct. Cc: Brandon Casey Cc: Marius Storm-Olsen Cc: Johannes Sixt Cc: Johannes Schindelin Cc: Ramsay Jones Cc: Gerrit Pape Cc: Petr Salinger Cc: Jonathan Nieder Acked-by: Thomas Schwinge (GNU Hurd changes) Signed-off-by: Kirill Smelkov Signed-off-by: Junio C Hamano --- Makefile | 6 ++++++ config.mak.uname | 10 ++++++++-- configure.ac | 8 ++++++++ git-compat-util.h | 8 ++++++++ 4 files changed, 30 insertions(+), 2 deletions(-) diff --git a/Makefile b/Makefile index dddaf4f287..03348066bc 100644 --- a/Makefile +++ b/Makefile @@ -30,6 +30,8 @@ all:: # Define LIBPCREDIR=/foo/bar if your libpcre header and library files are in # /foo/bar/include and /foo/bar/lib directories. # +# Define HAVE_ALLOCA_H if you have working alloca(3) defined in that header. +# # Define NO_CURL if you do not have libcurl installed. git-http-fetch and # git-http-push are not built, and you cannot use http:// and https:// # transports (neither smart nor dumb). @@ -1099,6 +1101,10 @@ ifdef USE_LIBPCRE EXTLIBS += -lpcre endif +ifdef HAVE_ALLOCA_H + BASIC_CFLAGS += -DHAVE_ALLOCA_H +endif + ifdef NO_CURL BASIC_CFLAGS += -DNO_CURL REMOTE_CURL_PRIMARY = diff --git a/config.mak.uname b/config.mak.uname index 7d31fad241..71602ee9a1 100644 --- a/config.mak.uname +++ b/config.mak.uname @@ -28,6 +28,7 @@ ifeq ($(uname_S),OSF1) NO_NSEC = YesPlease endif ifeq ($(uname_S),Linux) + HAVE_ALLOCA_H = YesPlease NO_STRLCPY = YesPlease NO_MKSTEMPS = YesPlease HAVE_PATHS_H = YesPlease @@ -35,6 +36,7 @@ ifeq ($(uname_S),Linux) HAVE_DEV_TTY = YesPlease endif ifeq ($(uname_S),GNU/kFreeBSD) + HAVE_ALLOCA_H = YesPlease NO_STRLCPY = YesPlease NO_MKSTEMPS = YesPlease HAVE_PATHS_H = YesPlease @@ -103,6 +105,7 @@ ifeq ($(uname_S),SunOS) NEEDS_NSL = YesPlease SHELL_PATH = /bin/bash SANE_TOOL_PATH = /usr/xpg6/bin:/usr/xpg4/bin + HAVE_ALLOCA_H = YesPlease NO_STRCASESTR = YesPlease NO_MEMMEM = YesPlease NO_MKDTEMP = YesPlease @@ -146,7 +149,7 @@ ifeq ($(uname_S),SunOS) endif INSTALL = /usr/ucb/install TAR = gtar - BASIC_CFLAGS += -D__EXTENSIONS__ -D__sun__ -DHAVE_ALLOCA_H + BASIC_CFLAGS += -D__EXTENSIONS__ -D__sun__ endif ifeq ($(uname_O),Cygwin) ifeq ($(shell expr "$(uname_R)" : '1\.[1-6]\.'),4) @@ -166,6 +169,7 @@ ifeq ($(uname_O),Cygwin) else NO_REGEX = UnfortunatelyYes endif + HAVE_ALLOCA_H = YesPlease NEEDS_LIBICONV = YesPlease NO_FAST_WORKING_DIRECTORY = UnfortunatelyYes NO_ST_BLOCKS_IN_STRUCT_STAT = YesPlease @@ -239,6 +243,7 @@ ifeq ($(uname_S),AIX) endif ifeq ($(uname_S),GNU) # GNU/Hurd + HAVE_ALLOCA_H = YesPlease NO_STRLCPY = YesPlease NO_MKSTEMPS = YesPlease HAVE_PATHS_H = YesPlease @@ -316,6 +321,7 @@ endif ifeq ($(uname_S),Windows) GIT_VERSION := $(GIT_VERSION).MSVC pathsep = ; + HAVE_ALLOCA_H = YesPlease NO_PREAD = YesPlease NEEDS_CRYPTO_WITH_SSL = YesPlease NO_LIBGEN_H = YesPlease @@ -363,7 +369,7 @@ ifeq ($(uname_S),Windows) COMPAT_OBJS = compat/msvc.o compat/winansi.o \ compat/win32/pthread.o compat/win32/syslog.o \ compat/win32/dirent.o - COMPAT_CFLAGS = -D__USE_MINGW_ACCESS -DNOGDI -DHAVE_STRING_H -DHAVE_ALLOCA_H -Icompat -Icompat/regex -Icompat/win32 -DSTRIP_EXTENSION=\".exe\" + COMPAT_CFLAGS = -D__USE_MINGW_ACCESS -DNOGDI -DHAVE_STRING_H -Icompat -Icompat/regex -Icompat/win32 -DSTRIP_EXTENSION=\".exe\" BASIC_LDFLAGS = -IGNORE:4217 -IGNORE:4049 -NOLOGO -SUBSYSTEM:CONSOLE -NODEFAULTLIB:MSVCRT.lib EXTLIBS = user32.lib advapi32.lib shell32.lib wininet.lib ws2_32.lib PTHREAD_LIBS = diff --git a/configure.ac b/configure.ac index 2f433939dc..0eae70430c 100644 --- a/configure.ac +++ b/configure.ac @@ -272,6 +272,14 @@ AS_HELP_STRING([], [ARG can be also prefix for libpcre library and hea GIT_CONF_SUBST([LIBPCREDIR]) fi) # +# Define HAVE_ALLOCA_H if you have working alloca(3) defined in that header. +AC_FUNC_ALLOCA +case $ac_cv_working_alloca_h in + yes) HAVE_ALLOCA_H=YesPlease;; + *) HAVE_ALLOCA_H='';; +esac +GIT_CONF_SUBST([HAVE_ALLOCA_H]) +# # Define NO_CURL if you do not have curl installed. git-http-pull and # git-http-push are not built, and you cannot use http:// and https:// # transports. diff --git a/git-compat-util.h b/git-compat-util.h index cbd86c37f5..63b2b3bb47 100644 --- a/git-compat-util.h +++ b/git-compat-util.h @@ -526,6 +526,14 @@ extern void release_pack_memory(size_t); typedef void (*try_to_free_t)(size_t); extern try_to_free_t set_try_to_free_routine(try_to_free_t); +#ifdef HAVE_ALLOCA_H +# include +# define xalloca(size) (alloca(size)) +# define xalloca_free(p) do {} while (0) +#else +# define xalloca(size) (xmalloc(size)) +# define xalloca_free(p) (free(p)) +#endif extern char *xstrdup(const char *str); extern void *xmalloc(size_t size); extern void *xmallocz(size_t size); -- 2.11.4.GIT