Reenable pwrite/pread support

The old checks supposed that pread/pwrite worked, if a declaration was
found in <unistd.h>.  We now actually check whether they work successfully
before using them.

3 files changed, 63 insertions, 55 deletions

diff --git a/acinclude.m4 b/acinclude.m4
index 7da512c2fd..3ebad7a5bb 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -374,80 +374,76 @@ X
     rm -fr conftest*
 ])
 
-AC_DEFUN(PHP_MISSING_PREAD_DECL,[
-  AC_CACHE_CHECK(whether pread works without custom declaration,ac_cv_pread,[
-  AC_TRY_COMPILE([#include <unistd.h>],[size_t (*func)() = pread],[
-    ac_cv_pread=yes
-  ],[
-    echo test > conftest_in
-    AC_TRY_RUN([
-#include <sys/types.h>
-#include <sys/stat.h>
-#include <fcntl.h>
-      main() { char buf[3]; return !(pread(open("conftest_in", O_RDONLY), buf, 2, 0) == 2); }
-    ],[
-      ac_cv_pread=yes
-    ],[
-      echo test > conftest_in
-      AC_TRY_RUN([
+AC_DEFUN(PHP_DOES_PWRITE_WORK,[
+  AC_TRY_RUN([
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
 #include <unistd.h>
-        ssize_t pread(int, void *, size_t, off64_t);
-        main() { char buf[3]; return !(pread(open("conftest_in", O_RDONLY), buf, 2, 0) == 2); }
-      ],[
-        ac_cv_pread=64
-      ],[
-        ac_cv_pread=no
-      ])
-    ],[
-      ac_cv_pread=no
-    ])
-  ])
+$1
+    main() { return !(pwrite(open("conftest_in", O_WRONLY|O_CREAT, 0600), "hi", 2, 0) == 2); }
+  ],[
+    ac_cv_pwrite=yes
+  ],[
+    ac_cv_pwrite=no
+  ],[
+    ac_cv_pwrite=no
   ])
-  case $ac_cv_pread in
-  no) ac_cv_func_pread=no;;
-  64) AC_DEFINE(PHP_PREAD_64, 1, [whether pread64 is default]);;
-  esac
 ])
 
-AC_DEFUN(PHP_MISSING_PWRITE_DECL,[
-  AC_CACHE_CHECK(whether pwrite works without custom declaration,ac_cv_pwrite,[
-  AC_TRY_COMPILE([#include <unistd.h>],[size_t (*func)() = pwrite],[
-    ac_cv_pwrite=yes
-  ],[
-    AC_TRY_RUN([
-#include <sys/types.h>
-#include <sys/stat.h>
-#include <fcntl.h>
-      main() { return !(pwrite(open("conftest_out", O_WRONLY|O_CREAT, 0600), "Ok", 2, 0) == 2); }
-    ],[
-      ac_cv_pwrite=yes
-    ],[
-      AC_TRY_RUN([
+AC_DEFUN(PHP_DOES_PREAD_WORK,[
+  echo test > conftest_in
+  AC_TRY_RUN([
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
 #include <unistd.h>
-        ssize_t pwrite(int, void *, size_t, off64_t);
-        main() { return !(pwrite(open("conftest_out", O_WRONLY|O_CREAT, 0600), "Ok", 2, 0) == 2); }
-      ],[
-        ac_cv_pwrite=64
-      ],[
-        ac_cv_pwrite=no
-      ])
-    ],[
-      ac_cv_pwrite=no
-    ])
+$1
+    main() { char buf[3]; return !(pread(open("conftest_in", O_RDONLY), buf, 2, 0) == 2); }
+  ],[
+    ac_cv_pread=yes
+  ],[
+    ac_cv_pread=no
+  ],[
+    ac_cv_pread=no
   ])
+  rm -f conftest_in
+])
+
+AC_DEFUN(PHP_PWRITE_TEST,[
+  AC_CACHE_CHECK(whether pwrite works,ac_cv_pwrite,[
+    PHP_DOES_PWRITE_WORK
+    if test "$ac_cv_pwrite" = "no"; then
+      PHP_DOES_PWRITE_WORK([ssize_t pwrite(int, void *, size_t, off64_t);])
+      if test "$ac_cv_pwrite" = "yes"; then
+        ac_cv_pwrite=64
+      fi
+    fi
   ])
+
   case $ac_cv_pwrite in
   no) ac_cv_func_pwrite=no;;
   64) AC_DEFINE(PHP_PWRITE_64, 1, [whether pwrite64 is default]);;
   esac
 ])
 
+AC_DEFUN(PHP_PREAD_TEST,[
+  AC_CACHE_CHECK(whether pread works,ac_cv_pread,[
+    PHP_DOES_PREAD_WORK
+    if test "$ac_cv_pread" = "no"; then
+      PHP_DOES_PREAD_WORK([ssize_t pread(int, void *, size_t, off64_t);])
+      if test "$ac_cv_pread" = "yes"; then
+        ac_cv_pread=64
+      fi
+    fi
+  ])
+
+  case $ac_cv_pread in
+  no) ac_cv_func_pread=no;;
+  64) AC_DEFINE(PHP_PREAD_64, 1, [whether pread64 is default]);;
+  esac
+])
+
 AC_DEFUN(PHP_MISSING_TIME_R_DECL,[
   AC_MSG_CHECKING([for missing declarations of reentrant functions])
   AC_TRY_COMPILE([#include <time.h>],[struct tm *(*func)() = localtime_r],[
diff --git a/ext/session/config.m4 b/ext/session/config.m4
index ddb92441ed..8bb43b676b 100644
--- a/ext/session/config.m4
+++ b/ext/session/config.m4
@@ -9,6 +9,9 @@ PHP_ARG_WITH(mm,for mm support,
 [  --with-mm[=DIR]         Include mm support for session storage], no, no)
 
 if test "$PHP_SESSION" != "no"; then
+  AC_CHECK_FUNCS(pread pwrite)
+  PHP_PWRITE_TEST
+  PHP_PREAD_TEST
   PHP_NEW_EXTENSION(session, session.c mod_files.c mod_mm.c mod_user.c, $ext_shared)
   PHP_SUBST(SESSION_SHARED_LIBADD)
   AC_DEFINE(HAVE_PHP_SESSION,1,[ ])
diff --git a/ext/session/mod_files.c b/ext/session/mod_files.c
index 2fce69d792..52dddadc6d 100644
--- a/ext/session/mod_files.c
+++ b/ext/session/mod_files.c
@@ -267,8 +267,13 @@ PS_READ_FUNC(files)
 	data->st_size = *vallen = sbuf.st_size;
 	*val = emalloc(sbuf.st_size);
 
+#ifdef HAVE_PREAD
+	n = pread(data->fd, *val, sbuf.st_size, 0);
+#else
 	lseek(data->fd, 0, SEEK_SET);
 	n = read(data->fd, *val, sbuf.st_size);
+#endif
+
 	if (n != sbuf.st_size) {
 		efree(*val);
 		return FAILURE;
@@ -294,8 +299,12 @@ PS_WRITE_FUNC(files)
 	if (vallen < (int)data->st_size)
 		ftruncate(data->fd, 0);
 
+#ifdef HAVE_PWRITE
+	n = pwrite(data->fd, val, vallen, 0);
+#else
 	lseek(data->fd, 0, SEEK_SET);
 	n = write(data->fd, val, vallen);
+#endif
 
 	if (n != vallen) {
 		php_error(E_WARNING, "write failed: %s (%d)", strerror(errno), errno);