Re: [PATCH] add __ASSUME_MREMAP

[Pino Toscano <toscano dot pino at tiscali dot it>]

Hi,

Alle martedì 15 gennaio 2013, Roland McGrath ha scritto:
> > -    HAVE_MREMAP                0 unless linux defined
> > +    HAVE_MREMAP                0 unless linux or __ASSUME_MREMAP
> > defined
> 
> Just simplify the condition to __ASSUME_MREMAP.
> We don't want anything like #ifdef linux in libc internals.

OK.

> But, I'm not really convinced that kernel-features.h is the right way
> to do this.  We have malloc-sysdep.h now, so that could just define
> HAVE_MREMAP directly.

I see, malloc-sysdep.h seems a better fit then, assuming it is fine 
using it outside of malloc itself.

> I do think it would be nice to have a single
> place define it rather than having both HAVE_REMAP for malloc and
> _G_HAVE_MREMAP for libio.

Yes, that is what my patch does. Attached there is a new version of it, 
updated after your feedback.

> But I never liked the use of
> kernel-features.h outside linux-specific files. OTOH, it is the
> status quo that it is used in a few generic files already. So
> perhaps using it a little more is not so bad.

I guess this would warrant an own discussion.

-- 
Pino Toscano

Add and use HAVE_MREMAP for mremap usage

Introduce a HAVE_MREMAP symbol to advertize mremap availability, and use
it also to replace _G_HAVE_MREMAP.

2013-01-15  Pino Toscano  <toscano.pino@tiscali.it>

	* sysdeps/unix/sysv/linux/malloc-sysdep.h (HAVE_MREMAP): New define.
	* malloc/malloc.c: Include <unistd.h> and <malloc-sysdep.h>.
	[!HAVE_MREMAP]: Remove [defined linux] case.
	* malloc/arena.c: Do not include <malloc-sysdep.h>.
	* libio/fileops.c [_LIBC]: Include <malloc-sysdep.h>.
        (mmap_remap_check) [defined _G_HAVE_MREMAP]: Change condition to
	[defined HAVE_MREMAP].
	* sysdeps/unix/sysv/linux/_G_config.h (_G_HAVE_MREMAP): Remove.

--- a/libio/fileops.c
+++ b/libio/fileops.c
@@ -46,6 +46,7 @@
 # include <shlib-compat.h>
 # include <not-cancel.h>
 # include <kernel-features.h>
+# include <malloc-sysdep.h>
 #endif
 #ifndef errno
 extern int errno;
@@ -650,7 +651,7 @@ mmap_remap_check (_IO_FILE *fp)
 	{
 	  /* The file added some pages.  We need to remap it.  */
 	  void *p;
-#ifdef _G_HAVE_MREMAP
+#ifdef HAVE_MREMAP
 	  p = __mremap (fp->_IO_buf_base, ROUNDED (fp->_IO_buf_end
 						   - fp->_IO_buf_base),
 			ROUNDED (st.st_size), MREMAP_MAYMOVE);
--- a/malloc/arena.c
+++ b/malloc/arena.c
@@ -19,9 +19,6 @@
 
 #include <stdbool.h>
 
-/* Get the implementation for check_may_shrink_heap.  */
-#include <malloc-sysdep.h>
-
 /* Compile-time constants.  */
 
 #define HEAP_MIN_SIZE (32*1024)
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -168,7 +168,7 @@
 
     Compilation Environment options:
 
-    HAVE_MREMAP                0 unless linux defined
+    HAVE_MREMAP                0
 
     Changing default word sizes:
 
@@ -214,8 +214,10 @@
 
 #include <stddef.h>   /* for size_t */
 #include <stdlib.h>   /* for getenv(), abort() */
+#include <unistd.h>   /* for __libc_enable_secure */
 
 #include <malloc-machine.h>
+#include <malloc-sysdep.h>
 
 #include <atomic.h>
 #include <_itoa.h>
@@ -490,19 +492,13 @@ void *(*__morecore)(ptrdiff_t) = __defau
 
 /*
   Define HAVE_MREMAP to make realloc() use mremap() to re-allocate
-  large blocks.  This is currently only possible on Linux with
-  kernel versions newer than 1.3.77.
+  large blocks.
 */
 
 #ifndef HAVE_MREMAP
-#ifdef linux
-#define HAVE_MREMAP 1
-#else
 #define HAVE_MREMAP 0
 #endif
 
-#endif /* HAVE_MREMAP */
-
 
 /*
   This version of malloc supports the standard SVID/XPG mallinfo
--- a/sysdeps/unix/sysv/linux/_G_config.h
+++ b/sysdeps/unix/sysv/linux/_G_config.h
@@ -46,7 +46,6 @@ typedef union
 #define _G_va_list __gnuc_va_list
 
 #define _G_HAVE_MMAP 1
-#define _G_HAVE_MREMAP 1
 
 #define _G_IO_IO_FILE_VERSION 0x20001
 
--- a/sysdeps/unix/sysv/linux/malloc-sysdep.h
+++ b/sysdeps/unix/sysv/linux/malloc-sysdep.h
@@ -55,3 +55,5 @@ check_may_shrink_heap (void)
 
   return may_shrink_heap;
 }
+
+#define HAVE_MREMAP 1

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