Add support for dynamically loading utimensat

This allows adding utimensat support in binaries for systems like
FreeBSD that only recently got it without dropping support for older
versions.

CMakeLists.txt

@@ -12,6 +12,7 @@ option(DEBUG_EXTRA "Expensive debug options" OFF)
 option(SET_WARNING_FLAGS "Adjust compiler warning flags" ON)
 option(SET_OPTIMIZATION_FLAGS "Adjust compiler optimization flags" ON)
 option(USE_CXX11 "Try to use C++11 if available" ON)
+option(USE_DYNAMIC_UTIMENSAT "Dynamically load utimensat if not available at compile time" OFF)
 if(NOT DEFINED DEBUG AND CMAKE_BUILD_TYPE STREQUAL "Debug")
 	set(DEBUG 1)
 endif()
@@ -210,11 +211,25 @@ if(NOT WIN32)
 	check_symbol_exists(ioctl "sys/ioctl.h" INNOEXTRACT_HAVE_IOCTL)
 	check_symbol_exists(timegm "time.h" INNOEXTRACT_HAVE_TIMEGM)
 	check_symbol_exists(gmtime_r "time.h" INNOEXTRACT_HAVE_GMTIME_R)
-	check_symbol_exists(utimensat "sys/stat.h" INNOEXTRACT_HAVE_UTIMENSAT)
 	check_symbol_exists(AT_FDCWD "fcntl.h" INNOEXTRACT_HAVE_AT_FDCWD)
+	if(INNOEXTRACT_HAVE_AT_FDCWD)
+		check_symbol_exists(utimensat "sys/stat.h" INNOEXTRACT_HAVE_UTIMENSAT)
+	endif()
 	if(INNOEXTRACT_HAVE_UTIMENSAT AND INNOEXTRACT_HAVE_AT_FDCWD)
 		set(INNOEXTRACT_HAVE_UTIMENSAT_d 1)
 	else()
+		if(USE_DYNAMIC_UTIMENSAT AND INNOEXTRACT_HAVE_AT_FDCWD)
+			set(CMAKE_REQUIRED_LIBRARIES ${CMAKE_DL_LIBS})
+			check_symbol_exists(dlsym "dlfcn.h" INNOEXTRACT_HAVE_DLSYM)
+			check_symbol_exists(RTLD_DEFAULT "dlfcn.h" INNOEXTRACT_HAVE_RTLD_DEFAULT)
+			unset(CMAKE_REQUIRED_LIBRARIES)
+			if(INNOEXTRACT_HAVE_DLSYM AND INNOEXTRACT_HAVE_RTLD_DEFAULT)
+				set(INNOEXTRACT_HAVE_DYNAMIC_UTIMENSAT 1)
+				if(CMAKE_DL_LIBS)
+					list(APPEND LIBRARIES ${CMAKE_DL_LIBS})
+				endif()
+			endif()
+		endif()
 		check_symbol_exists(utimes "sys/time.h" INNOEXTRACT_HAVE_UTIMES)
 	endif()
 	
@@ -407,11 +422,15 @@ print_configuration("LZMA decompression" FIRST
 	INNOEXTRACT_HAVE_LZMA "enabled"
 	1                     "disabled"
 )
+if(INNOEXTRACT_HAVE_DYNAMIC_UTIMENSAT)
+	set(time_prefix "nanoseconds if supported, ")
+	set(time_suffix " otherwise")
+endif()
 print_configuration("File time precision" FIRST
 	INNOEXTRACT_HAVE_UTIMENSAT_d "nanoseconds"
 	WIN32                        "100-nanoseconds"
-	INNOEXTRACT_HAVE_UTIMES      "microseconds"
-	1                            "seconds"
+	INNOEXTRACT_HAVE_UTIMES      "${time_prefix}microseconds${time_suffix}"
+	1                            "${time_prefix}seconds${time_suffix}"
 )
 print_configuration("Charset conversion"
 	INNOEXTRACT_HAVE_ICONV        "iconv"

README.md

@@ -51,6 +51,7 @@ Build options:
 | `SET_WARNING_FLAGS`      | `ON`      | Adjust compiler warning flags. This should not affect the produced binaries but is useful to catch potential problems.
 | `SET_OPTIMIZATION_FLAGS` | `ON`      | Adjust compiler optimization flags. For non-debug builds the only thing this does is instruct the linker to only link against libraries that are actually needed.
 | `USE_CXX11`              | `ON`      | Try to compile in C++11 mode if available.
+| `USE_DYNAMIC_UTIMENSAT`  | `OFF`     | Dynamically load utimensat(2) if not available at compile time
 | `USE_STATIC_LIBS`        | `OFF`^3   | Turns on static linking for all libraries, including `-static-libgcc` and `-static-libstdc++`. You can also use the individual options below:
 | `LZMA_USE_STATIC_LIBS`   | `OFF`^4   | Statically link `liblzma`.
 | `Boost_USE_STATIC_LIBS`  | `OFF`^4   | Statically link Boost. See also `FindBoost.cmake`

src/configure.hpp.in

@@ -12,9 +12,13 @@
 
 // File functions
 #cmakedefine01 INNOEXTRACT_HAVE_UTIMENSAT
+#cmakedefine01 INNOEXTRACT_HAVE_DYNAMIC_UTIMENSAT
 #cmakedefine01 INNOEXTRACT_HAVE_AT_FDCWD
 #cmakedefine01 INNOEXTRACT_HAVE_UTIMES
 
+// Shared functions
+#cmakedefine01 INNOEXTRACT_HAVE_DLSYM
+
 // Endianness
 #cmakedefine01 INNOEXTRACT_HAVE_BUILTIN_BSWAP16
 #cmakedefine01 INNOEXTRACT_HAVE_BUILTIN_BSWAP32

src/util/time.cpp

@@ -32,9 +32,16 @@
 #include <windows.h>
 #endif
 
+#if INNOEXTRACT_HAVE_DLSYM
+#include <dlfcn.h>
+#endif
+
+#if INNOEXTRACT_HAVE_AT_FDCWD
+#include <fcntl.h>
+#endif
+
 #if INNOEXTRACT_HAVE_UTIMENSAT && INNOEXTRACT_HAVE_AT_FDCWD
 #include <sys/stat.h>
-#include <fcntl.h>
 #elif !defined(_WIN32) && INNOEXTRACT_HAVE_UTIMES
 #include <sys/time.h>
 #elif !defined(_WIN32)
@@ -246,18 +253,37 @@ static HANDLE open_file(LPCWSTR name) {
 
 #endif
 
+#if INNOEXTRACT_HAVE_DYNAMIC_UTIMENSAT
+extern "C" typedef int (*utimensat_proc)
+	(int fd, const char *path, const struct timespec times[2], int flag);
+#endif
+
 bool set_file_time(const boost::filesystem::path & path, time t, boost::uint32_t nsec) {
 	
-#if INNOEXTRACT_HAVE_UTIMENSAT && INNOEXTRACT_HAVE_AT_FDCWD
+#if (INNOEXTRACT_HAVE_DYNAMIC_UTIMENSAT || INNOEXTRACT_HAVE_UTIMENSAT) \
+    && INNOEXTRACT_HAVE_AT_FDCWD
 	
 	// nanosecond precision, for Linux and POSIX.1-2008+ systems
 	
-	struct timespec times[2];
-	times[0].tv_sec = to_time_t<time_t>(t, path.string().c_str());
-	times[0].tv_nsec = boost::int32_t(nsec);
-	times[1] = times[0];
+	struct timespec timens[2];
+	timens[0].tv_sec = to_time_t<time_t>(t, path.string().c_str());
+	timens[0].tv_nsec = boost::int32_t(nsec);
+	timens[1] = timens[0];
+	
+#endif
+	
+#if INNOEXTRACT_HAVE_DYNAMIC_UTIMENSAT && INNOEXTRACT_HAVE_AT_FDCWD
+	
+	static utimensat_proc utimensat_func = (utimensat_proc)dlsym(RTLD_DEFAULT, "utimensat");
+	if(utimensat_func) {
+		return (utimensat_func(AT_FDCWD, path.string().c_str(), timens, 0) == 0);
+	}
+	
+#endif
+	
+#if INNOEXTRACT_HAVE_UTIMENSAT && INNOEXTRACT_HAVE_AT_FDCWD
 	
-	return (utimensat(AT_FDCWD, path.string().c_str(), times, 0) == 0);
+	return (utimensat(AT_FDCWD, path.string().c_str(), timens, 0) == 0);
 	
 #elif defined(_WIN32)