* configure.in (RUBY_CHECK_IO_NEED): check whether fseek() and

  fflush() are needed.

* io.c (flush_before_seek): flush write stream only.

* io.c (rb_io_check_readable): seek instead of flush if the last
  operation was write.

* io.c (rb_io_check_writable): seek instead of flush if the last
  operation was read.

* bcc32/Makefile.sub, win32/Makefile.sub: needs to seek between
  R/W.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@3318 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 29 insertions, 15 deletions

diff --git a/configure.in b/configure.in
index b6bc0a03d4..1619b798df 100644
--- a/configure.in
+++ b/configure.in
@@ -265,14 +265,14 @@ darwin*)	LIBS="-lobjc $LIBS";;
 human*)		ac_cv_func_getpgrp_void=yes;;
 beos*)		;;
 cygwin*)	rb_cv_have_daylight=no
-		rb_cv_need_io_flush_between_rw=no
+		rb_cv_need_io_seek_between_rw=no
 		rb_cv_need_io_flush_before_seek=no
 		ac_cv_var_tzname=no
 		ac_cv_func__setjmp=no
 		ac_cv_func_setitimer=no
 		;;
 mingw*)		LIBS="-lwsock32 $LIBS"
-		rb_cv_need_io_flush_between_rw=yes
+		rb_cv_need_io_seek_between_rw=yes
 		rb_cv_need_io_flush_before_seek=no
 		ac_cv_header_a_out_h=no
 		ac_cv_header_pwd_h=no
@@ -559,10 +559,19 @@ else
   fi
 fi
 
-AC_DEFUN(RUBY_CHECK_IO_NEED_FLUSH,
-[AC_CACHE_CHECK(whether need to flush [$1], [$2],
+AC_DEFUN(RUBY_CHECK_IO_NEED,
+[AC_CACHE_CHECK(whether need to [$1], [$2],
     [AC_TRY_RUN([
 #include <stdio.h>
+#ifndef SEEK_SET
+#define SEEK_SET 0
+#endif
+#ifndef SEEK_CUR
+#define SEEK_CUR 1
+#endif
+#define before_seek(f) ]ifelse(index($2,flush_before_seek),-1,[fflush(f)],[(f,0)])[
+#define reset_rw(f) ]ifelse(index($2,seek_between_rw),-1,[do_seek(f,SEEK_CUR)],[(f,0)])[
+#define do_seek(f, w) (before_seek(f), fseek(f,0,w))
 
 char *fn = "conftest.dat";
 char *wombat = "wombat\n";
@@ -576,14 +585,11 @@ int main()
 
     if (!(f = fopen(fn, "w+"))) return 1;
     fputs(wombat, f);
-    fflush(f);
-    fseek(f, 0, 0);
+    do_seek(f, SEEK_SET);
     if (!fgets(buf, BUFSIZ, f) || strcmp(buf, wombat)) goto fail;
-    ]ifelse(index($2,between_rw),-1,fflush(f);)[
+    reset_rw(f);
     fputs(koara, f);
-    ]ifelse(index($2,before_seek),-1,fflush(f);)[
-    fseek(f, 0, 0);
-    ]ifelse(index($2,between_rw),-1,fflush(f);)[
+    do_seek(f, SEEK_SET);
     if (!fgets(buf, BUFSIZ, f) || strcmp(buf, wombat)) goto fail;
     if (!fgets(buf, BUFSIZ, f) || strcmp(buf, koara)) goto fail;
     r = 0;
@@ -593,14 +599,22 @@ int main()
     return r;
 }
 ], [$2]=no, [$2]=yes, [$2]=yes)])])
-
-RUBY_CHECK_IO_NEED_FLUSH(between R/W, rb_cv_need_io_flush_between_rw)
-RUBY_CHECK_IO_NEED_FLUSH(before seek, rb_cv_need_io_flush_before_seek)
-if test "$rb_cv_need_io_flush_between_rw" = yes; then
-  AC_DEFINE(NEED_IO_FLUSH_BETWEEN_RW, 1)
+RUBY_CHECK_IO_NEED(seek between R/W, rb_cv_need_io_seek_between_rw)
+RUBY_CHECK_IO_NEED(flush before seek, rb_cv_need_io_flush_before_seek)
+check_to_do_something_else=no
+if test "$rb_cv_need_io_seek_between_rw" = yes; then
+  AC_DEFINE(NEED_IO_SEEK_BETWEEN_RW, 1)
+  check_to_do_something_else=yes
 fi
 if test "$rb_cv_need_io_flush_before_seek" = yes; then
   AC_DEFINE(NEED_IO_FLUSH_BEFORE_SEEK, 1)
+  check_to_do_something_else=yes
+fi
+if test "$cross_compiling" = no -a "$check_to_do_something_else" = yes; then
+  RUBY_CHECK_IO_NEED(do something else, unexpected_stdio_behavior)
+  if test "$unexpected_stdio_behavior" = yes; then
+    AC_MSG_FAILURE([unexpected stdio behavior])
+  fi
 fi
 
 dnl default value for $KANJI