[glibc] glibc.malloc.check: Fix nit in documentation

[Siddhesh Poyarekar <siddhesh@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=83e55c982ffcf42185254cff5ac16377672ae32e

commit 83e55c982ffcf42185254cff5ac16377672ae32e
Author: Siddhesh Poyarekar <siddhesh@sourceware.org>
Date:   Wed Jul 7 07:02:13 2021 +0530

    glibc.malloc.check: Fix nit in documentation
    
    The tunable will not work with *any* non-zero tunable value since its
    list of allowed values is 0-3.  Fix the documentation to reflect that.
    
    Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

Diff:
---
 manual/memory.texi   | 10 +++++-----
 manual/tunables.texi |  2 +-
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/manual/memory.texi b/manual/memory.texi
index 28ec2e4e63..31ee36be8c 100644
--- a/manual/memory.texi
+++ b/manual/memory.texi
@@ -1364,11 +1364,11 @@ The block was already freed.
 Another possibility to check for and guard against bugs in the use of
 @code{malloc}, @code{realloc} and @code{free} is to set the environment
 variable @code{MALLOC_CHECK_}.  When @code{MALLOC_CHECK_} is set to a
-non-zero value, a special (less efficient) implementation is used which
-is designed to be tolerant against simple errors, such as double calls
-of @code{free} with the same argument, or overruns of a single byte
-(off-by-one bugs).  Not all such errors can be protected against,
-however, and memory leaks can result.
+non-zero value less than 4, a special (less efficient) implementation is
+used which is designed to be tolerant against simple errors, such as
+double calls of @code{free} with the same argument, or overruns of a
+single byte (off-by-one bugs).  Not all such errors can be protected
+against, however, and memory leaks can result.
 
 Any detected heap corruption results in immediate termination of the
 process.
diff --git a/manual/tunables.texi b/manual/tunables.texi
index d5d957fb5b..ebdb562e36 100644
--- a/manual/tunables.texi
+++ b/manual/tunables.texi
@@ -115,7 +115,7 @@ following tunables in the @code{malloc} namespace:
 This tunable supersedes the @env{MALLOC_CHECK_} environment variable and is
 identical in features.
 
-Setting this tunable to a non-zero value enables a special (less
+Setting this tunable to a non-zero value less than 4 enables a special (less
 efficient) memory allocator for the @code{malloc} family of functions that is
 designed to be tolerant against simple errors such as double calls of
 free with the same argument, or overruns of a single byte (off-by-one