This patch fixes a crash in the libxml2 bindings for Python 3.x
that 'itstool' stumbles upon when processing UTF-8 data:

  https://issues.guix.gnu.org/issue/37468

Patch by Jan Matejek
from <https://bugzilla.opensuse.org/show_bug.cgi?id=1065270>.

--- libxml2-2.9.5.orig/python/libxml.c
+++ libxml2-2.9.5/python/libxml.c
@@ -1620,6 +1620,7 @@ libxml_xmlErrorFuncHandler(ATTRIBUTE_UNU
     PyObject *message;
     PyObject *result;
     char str[1000];
+    unsigned char *ptr = (unsigned char *)str;
 
 #ifdef DEBUG_ERROR
     printf("libxml_xmlErrorFuncHandler(%p, %s, ...) called\n", ctx, msg);
@@ -1636,12 +1637,20 @@ libxml_xmlErrorFuncHandler(ATTRIBUTE_UNU
 	    str[999] = 0;
         va_end(ap);
 
+#if PY_MAJOR_VERSION >= 3
+        /* Ensure the error string doesn't start at UTF8 continuation. */
+        while (*ptr && (*ptr & 0xc0) == 0x80)
+            ptr++;
+#endif
+
         list = PyTuple_New(2);
         PyTuple_SetItem(list, 0, libxml_xmlPythonErrorFuncCtxt);
         Py_XINCREF(libxml_xmlPythonErrorFuncCtxt);
-        message = libxml_charPtrConstWrap(str);
+        message = libxml_charPtrConstWrap(ptr);
         PyTuple_SetItem(list, 1, message);
         result = PyEval_CallObject(libxml_xmlPythonErrorFuncHandler, list);
+        /* Forget any errors caused in the error handler. */
+        PyErr_Clear();
         Py_XDECREF(list);
         Py_XDECREF(result);
     }
>log</a><a href='/guix/tree/gnu/packages/patches/llvm-9-fix-bitcast-miscompilation.patch?id=a44569899a54d18a70b62498bec3774f0be3f66b'>tree</a><a href='/guix/commit/gnu/packages/patches/llvm-9-fix-bitcast-miscompilation.patch?id=a44569899a54d18a70b62498bec3774f0be3f66b'>commit</a><a href='/guix/diff/gnu/packages/patches/llvm-9-fix-bitcast-miscompilation.patch?id=a44569899a54d18a70b62498bec3774f0be3f66b'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/gnu/packages/patches/llvm-9-fix-bitcast-miscompilation.patch'>
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<div class='path'>path: <a href='/guix/log/?id=a44569899a54d18a70b62498bec3774f0be3f66b&amp;showmsg=1'>root</a>/<a href='/guix/log/gnu?id=a44569899a54d18a70b62498bec3774f0be3f66b&amp;showmsg=1'>gnu</a>/<a href='/guix/log/gnu/packages?id=a44569899a54d18a70b62498bec3774f0be3f66b&amp;showmsg=1'>packages</a>/<a href='/guix/log/gnu/packages/patches?id=a44569899a54d18a70b62498bec3774f0be3f66b&amp;showmsg=1'>patches</a>/<a href='/guix/log/gnu/packages/patches/llvm-9-fix-bitcast-miscompilation.patch?id=a44569899a54d18a70b62498bec3774f0be3f66b&amp;showmsg=1'>llvm-9-fix-bitcast-miscompilation.patch</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/packages/patches/llvm-9-fix-bitcast-miscompilation.patch?id=a44569899a54d18a70b62498bec3774f0be3f66b'>Collapse</a>)</th><th class='left'>Author</th></tr>
<tr class='logheader'><td><span title='2020-11-14 11:41:07 -0500'>2020-11-14</span></td><td class='logsubject'><a href='/guix/commit/gnu/packages/patches/llvm-9-fix-bitcast-miscompilation.patch?id=9e4c24ef90545e242539a16a5ea28d7effc45933'>gnu: llvm-9: Standardize patch level.</a></td><td>Maxim Cournoyer</td></tr>
<tr class='nohover-highlight'><td/><td colspan='3' class='logmsg'>
Having a non-standard (different than 1) patch level requirement means the
patches cannot be composed easily from different origins.  The following
command was used to remove one level from the llvm-9 patches:

  sed -e 's|^--- a/|--- |' -e 's|^+++ b/|+++ |' \
      gnu/packages/patches/llvm-9* -i

* gnu/packages/llvm.scm (llvm-9)[source]: Drop the patch-flags field.
Re-indent list of patches.
* gnu/packages/patches/llvm-9-fix-bitcast-miscompilation.patch: Strip one level.
* gnu/packages/patches/llvm-9-fix-lpad-miscompilation.patch: Likewise.
* gnu/packages/patches/llvm-9-fix-scev-miscompilation.patch: Likewise.


</td></tr>
<tr class='logheader'><td><span title='2020-07-03 01:26:16 +0200'>2020-07-03</span></td><td class='logsubject'><a href='/guix/commit/gnu/packages/patches/llvm-9-fix-bitcast-miscompilation.patch?id=ff2f86114c0d250351661a81bb95c627141179d8'>gnu: llvm-9: Backport patch to fix miscompilation for big-endian targets.</a></td><td>Jakub Kądziołka</td></tr>
<tr class='nohover-highlight'><td/><td colspan='3' class='logmsg'>
* gnu/packages/llvm.scm (llvm-9)[source]: Add new patch.
* gnu/packages/patches/llvm-9-fix-bitcast-miscompilation.patch: New file.
* gnu/local.mk (dist_patch_DATA): Register new file.


</td></tr>