lim_data too narrow

lim_data too narrow

[James Van Artsdalen]

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Please write in English, because the Emacs maintainers do not have
translators to read other languages for them.

In GNU Emacs 21.3 (amd64--freebsd)

lim_data is too narrow to hold the size of the process data segment.
On my system (with 8 GB of RAM) the rlimit is by default (in KB):

$ ulimit -d
8388608

lim_data needs to be at least as wide as the rlimit .rlim_cur field or
truncation occurs.

I'm not sure what the right cross-platform portable way to detect this
situation is.  The patch below is an example.

Note that this change is not sufficient to build emacs for amd64.

*** mem-limits.h.~1~    Wed Mar  8 12:49:46 2000
--- mem-limits.h        Wed Dec 17 03:15:24 2003
***************
*** 98,104 ****
  static POINTER data_space_start;
  
  /* Number of bytes of writable memory we can expect to be able to get */
! static unsigned long lim_data;
  
  #ifdef NO_LIM_DATA
  static void
--- 98,104 ----
  static POINTER data_space_start;
  
  /* Number of bytes of writable memory we can expect to be able to get */
! static rlim_t lim_data;
  
  #ifdef NO_LIM_DATA
  static void

Re: lim_data too narrow

[Richard Stallman]

    lim_data needs to be at least as wide as the rlimit .rlim_cur field or
    truncation occurs.

It would seem that on a 64-bit machine, lim_data should
be a 64-bit type.  Is there any agreement on how to
specify such a type in C?

We could use configure to check whether rlim_t is defined
in some header file.  What header file should it be in?

Re: lim_data too narrow

[Eli Zaretskii]

> From: Richard Stallman <rms@gnu.org>
> Date: Sun, 21 Dec 2003 23:07:56 -0500
> 
> It would seem that on a 64-bit machine, lim_data should
> be a 64-bit type.  Is there any agreement on how to
> specify such a type in C?

Modern compilers should support the int64_t type (it is mandated by
the new C99 standard and should be defined on stdint.h).

> We could use configure to check whether rlim_t is defined
> in some header file.  What header file should it be in?

According to Posix, it should be in sys/resource.h.

Re: lim_data too narrow

[Richard Stallman]

    Modern compilers should support the int64_t type (it is mandated by
    the new C99 standard and should be defined on stdint.h).

Do we want it to be 64 bits on all machines?  I suppose it would
not do any great harm.

    > We could use configure to check whether rlim_t is defined
    > in some header file.  What header file should it be in?

    According to Posix, it should be in sys/resource.h.

In that case, let's make configure check that rlim_t is really
defined, and use it if it is defined.

Re: lim_data too narrow

[Stefan Monnier]

>> It would seem that on a 64-bit machine, lim_data should
>> be a 64-bit type.  Is there any agreement on how to
>> specify such a type in C?

> Modern compilers should support the int64_t type (it is mandated by
> the new C99 standard and should be defined on stdint.h).

Wouldn't something like size_t be preferable?


        Stefan