Bryan O'Sullivan  committed 80004b5

Update the README with pointers to the double-conversion workaround.

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File README.markdown

-# Welcome to aeson
+# Welcome to blaze-textual
 blaze-textual is a fast Haskell library for rendering common Haskell
 datatypes in text form using the
+# Important note for users of GHCi and Template Haskell
+To achieve excellent performance for rendering floating point numbers,
+this package uses the
+Unfortunately, due to bugs in GHC, some uses of GHCi and Template
+Haskell can crash if this package is loaded.
+* [5289: Can't use ghci with a library linked against
+  libstdc++]( (fixed
+  in GHC 7.2.1).
+* [5386: GHCi crashes with SIGFPE when using double-conversion
+  package]( (not yet
+  fixed at the time of writing)
+If you are affected by these problems, you should expect the 5289
+crash to look like this:
+    Loading package double-conversion- ... can't load .so/.DLL for: stdc++
+The 5386 crash causes GHCi to die with a floating point exception
+To work around these bugs, this package includes an alternative,
+slower, floating point conversion that is written in pure Haskell.
+Because it is 10 times slower than the double-conversion package, it
+is not the default.
+To use it, reinstall this package by passing the `native` flag to
+    cabal install -fnative
+Afterwards, you will also need to reinstall any downstream packages
+that depend on this one, e.g. the [aeson JSON
+    cabal install aeson --reinstall
 # Join in!
 We are happy to receive bug reports, fixes, documentation

File blaze-textual.cabal

     A library for efficiently rendering Haskell datatypes to
+    .
+    /Note/: if you use GHCi or Template Haskell, please see the
+    @README@ file for important details about building this package,
+    and other packages that depend on it:
+    <>
+    tests/*.hs
 flag developer
   description: operate in developer mode