From: Paul Floyd <pjfloyd@wanadoo.fr>
Date: Sun, 21 Sep 2025 18:53:33 +0000 (+0200)
Subject: Doc: add item on tcmalloc >= 2.16 hangs to FAQ
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=b5c89ee9839a356248e7fc8f406d7ef888d76076;p=thirdparty%2Fvalgrind.git

Doc: add item on tcmalloc >= 2.16 hangs to FAQ
---

diff --git a/docs/xml/FAQ.xml b/docs/xml/FAQ.xml
index 201b36502..f246fa6c9 100644
--- a/docs/xml/FAQ.xml
+++ b/docs/xml/FAQ.xml
@@ -541,6 +541,26 @@ int main(void)
   </answer>
 </qandaentry>
 
+<qandaentry id="faq.hangs">
+  <question id="q-hangs">
+    <para>Why does Valgrind hang when using tcmalloc?</para>
+  </question>
+  <answer id="a-hangss">
+    <para>This is because tcmalloc makes a recursive call in its initialisation code.
+      Under Valgrind that becomes either an infinite loop with optimised builds of tcmalloc
+      or a stack overflow crash with debug builds of it.</para>
+
+    <para>Your options are:
+      <itemizedlist>
+        <listitem>Do not use tcmalloc in the builds that you test with Valgrind.</listitem>
+        <listitem>Use an older version of tcmalloc. This problem started on 2024-03-24.
+          If you use gperftools 2.15 or older you should not have this problem.</listitem>
+      </para>
+
+  </answer>
+</qandaentry>
+
+
 </qandadiv>
 
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