Document brk segment limitation, reference manual in limit reached msg.

The msg telling brk cannot be extended confuses some users
so improve the documentation and have the msg referencing the doc.

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@15880

diff --git a/NEWS b/NEWS
index 56bbee39eaf4a2755fe6153a6fa41c22785263c0..0895f8c8f9babd9e172bae883cf68084a5948d9e 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -107,6 +107,7 @@ n-i-bz Fix incorrect (or infinite loop) unwind on RHEL7 x86 and amd64
 n-i-bz massif --pages-as-heap=yes does not report peak caused by mmap+munmap
 n-i-bz false positive leaks due to aspacemgr merging non heap segments with heap segments.
 n-i-bz Fix ppoll_alarm exclusion on OS X
+n-i-bz Document brk segment limitation, reference manual in limit reached msg.
 
 Release 3.11.0 (22 September 2015)
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

diff --git a/coregrind/m_syswrap/syswrap-generic.c b/coregrind/m_syswrap/syswrap-generic.c
index dd1da9c3f00185ca69d18be0b8f4d1f2101bc916..ed444943504ae364a9e50c087afc02ca8046544f 100644 (file)
--- a/coregrind/m_syswrap/syswrap-generic.c
+++ b/coregrind/m_syswrap/syswrap-generic.c
@@ -1324,6 +1324,7 @@ static Addr do_brk ( Addr newbrk, ThreadId tid )
       else
          VG_(umsg)("Cannot map memory to grow brk segment in thread #%u "
                    "to %#lx\n", tid, newbrkP);
+      VG_(umsg)("(see section Limitations in user manual)\n");
       goto bad;
    }
 

diff --git a/docs/xml/manual-core.xml b/docs/xml/manual-core.xml
index 762883666910e92539f005ff2d9bb4cdc17fdc87..34cb2c6bc94c8c7cb10ea54f89fadf78ea3311a8 100644 (file)
--- a/docs/xml/manual-core.xml
+++ b/docs/xml/manual-core.xml
@@ -2778,6 +2778,18 @@ programs actually work fine.</para>
 subject to the following constraints:</para>
 
  <itemizedlist>
+  <listitem>
+    <para>Valgrind determines at startup the size of the 'brk segment'
+      using the RLIMIT_DATA rlim_cur, with a minimum of 1 MB and a
+      maximum of 8 MB. Valgrind outputs a message each time a program
+      tries to extend the brk segment beyond the size determined at
+      startup.  Most programs will work properly with this limit,
+      typically by switching to the use of mmap to get more memory.
+      If your program really needs a big brk segment, you must change
+      the 8 MB hardcoded limit and recompile Valgrind.
+   </para>
+  </listitem>
+
   <listitem>
    <para>On x86 and amd64, there is no support for 3DNow!
    instructions.  If the translator encounters these, Valgrind will

diff --git a/memcheck/tests/linux/brk.stderr.exp b/memcheck/tests/linux/brk.stderr.exp
index 17d8a703d549dbf6dd2dac5f20a761b06721e047..8cbe6223783c23ad1e9a95b7a2711b5f1dcb4090 100644 (file)
--- a/memcheck/tests/linux/brk.stderr.exp
+++ b/memcheck/tests/linux/brk.stderr.exp
@@ -1,6 +1,8 @@
 
 brk segment overflow in thread #1: can't grow to 0x........
+(see section Limitations in user manual)
 brk segment overflow in thread #1: can't grow to 0x........
+(see section Limitations in user manual)
 
 HEAP SUMMARY:
     in use at exit: ... bytes in ... blocks

diff --git a/none/tests/linux/brk-overflow1.stderr.exp b/none/tests/linux/brk-overflow1.stderr.exp
index f1315792ee01650b1e4fd7d357fee7e03c41baca..96741db856134d72b4dc6f674ec59a71bd383dde 100644 (file)
--- a/none/tests/linux/brk-overflow1.stderr.exp
+++ b/none/tests/linux/brk-overflow1.stderr.exp
@@ -1,3 +1,4 @@
 
 brk segment overflow in thread #1: can't grow to 0x........
+(see section Limitations in user manual)
 

diff --git a/none/tests/linux/brk-overflow2.stderr.exp b/none/tests/linux/brk-overflow2.stderr.exp
index df6285842f9bdfc3b65d9beea75cc3900d5c88cc..5cdf1f7c345d122921af8f31e054fb5b63b2bb51 100644 (file)
--- a/none/tests/linux/brk-overflow2.stderr.exp
+++ b/none/tests/linux/brk-overflow2.stderr.exp
@@ -1,5 +1,8 @@
 
 brk segment overflow in thread #1: can't grow to 0x........
+(see section Limitations in user manual)
 brk segment overflow in thread #1: can't grow to 0x........
+(see section Limitations in user manual)
 brk segment overflow in thread #1: can't grow to 0x........
+(see section Limitations in user manual)