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 <alloca.h>
# 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 <drafnel@xxxxxxxxx>
Cc: Marius Storm-Olsen <mstormo@xxxxxxxxx>
Cc: Johannes Sixt <j6t@xxxxxxxx>
Cc: Johannes Schindelin <Johannes.Schindelin@xxxxxx>
Cc: Ramsay Jones <ramsay@xxxxxxxxxxxxxxxxxxx>
Cc: Gerrit Pape <pape@xxxxxxxxxxx>
Cc: Petr Salinger <Petr.Salinger@xxxxxxxxx>
Cc: Jonathan Nieder <jrnieder@xxxxxxxxx>
Cc: Thomas Schwinge <tschwinge@xxxxxxx>
Signed-off-by: Kirill Smelkov <kirr@xxxxxxxxxx>
---
( new patch )
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 dddaf4f..0334806 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 7d31fad..71602ee 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 2f43393..0eae704 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 cbd86c3..63b2b3b 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 <alloca.h>
+# 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);
--
1.9.rc1.181.g641f458
--
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