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authorSverker Eriksson <[email protected]>2017-02-28 14:52:08 +0100
committerSverker Eriksson <[email protected]>2017-02-28 14:52:08 +0100
commit1b3b07e78580435477eec4d8558e91167b7c03aa (patch)
tree6714497790d1adc9fc768e1d9cca5afe87e77bb1 /erts
parente6059f94571a6c968c15b9de6b7d63ebd64f9acf (diff)
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zlib: Add warning for option WindowBits values 8 and -8.
Diffstat (limited to 'erts')
-rw-r--r--erts/doc/src/zlib.xml9
1 files changed, 9 insertions, 0 deletions
diff --git a/erts/doc/src/zlib.xml b/erts/doc/src/zlib.xml
index 138414a880..583d21ad7b 100644
--- a/erts/doc/src/zlib.xml
+++ b/erts/doc/src/zlib.xml
@@ -315,6 +315,15 @@ list_to_binary([B1,B2])</pre>
<c><anno>WindowBits</anno></c> value suppresses the zlib header
(and checksum) from the stream. Notice that the zlib source
mentions this only as a undocumented feature.</p>
+ <warning>
+ <p>Due to a known bug in zlib, <c>WindowsBits</c> values 8 and -8
+ do not work as expected. In zlib versions before 1.2.9 values
+ 8 and -8 are automatically changed to 9 and -9. <em>From zlib version 1.2.9
+ value -8 is rejected</em> causing <c>zlib:deflateInit/6</c> to fail
+ (8 is still changed to 9). It also seem possible that future versions
+ of zlib may fix this bug and start accepting 8 and -8 as is.</p>
+ <p>Conclusion: Avoid values 8 and -8 unless you know your zlib version supports them.</p>
+ </warning>
</item>
<tag><c><anno>MemLevel</anno></c></tag>
<item>