From 13c6828bedeb815ee7748f82ca36073dbd55a9db Mon Sep 17 00:00:00 2001
From: Colin Cross <ccross@android.com>
Date: Thu, 15 Sep 2022 21:58:24 +0000
Subject: [PATCH] Fix std::fpos pretty printer on musl

The mbstate_t field in std::fpos is an opaque type provied by libc,
and musl's implementation does not match the one used by glibc.
Change StdFposPrinter to verify its assumptions about the layout
of mbstate_t, and leave out the state printing if it doesn't match.

Reviewed By: #libc, ldionne

Differential Revision: https://reviews.llvm.org/D132983
---
 .../libcxx/gdb/gdb_pretty_printer_test.sh.cpp    |  9 +++------
 libcxx/utils/gdb/libcxx/printers.py              | 16 ++++++++++++----
 2 files changed, 15 insertions(+), 10 deletions(-)

diff --git a/libcxx/test/libcxx/gdb/gdb_pretty_printer_test.sh.cpp b/libcxx/test/libcxx/gdb/gdb_pretty_printer_test.sh.cpp
index 511fe24675a2..3a4e544ae8c8 100644
--- a/libcxx/test/libcxx/gdb/gdb_pretty_printer_test.sh.cpp
+++ b/libcxx/test/libcxx/gdb/gdb_pretty_printer_test.sh.cpp
@@ -643,17 +643,14 @@ void shared_ptr_test() {
 
 void streampos_test() {
   std::streampos test0 = 67;
-  ComparePrettyPrintToChars(
-      test0, "std::fpos with stream offset:67 with state: {count:0 value:0}");
+  ComparePrettyPrintToRegex(test0, "^std::fpos with stream offset:67( with state: {count:0 value:0})?$");
   std::istringstream input("testing the input stream here");
   std::streampos test1 = input.tellg();
-  ComparePrettyPrintToChars(
-      test1, "std::fpos with stream offset:0 with state: {count:0 value:0}");
+  ComparePrettyPrintToRegex(test1, "^std::fpos with stream offset:0( with state: {count:0 value:0})?$");
   std::unique_ptr<char[]> buffer(new char[5]);
   input.read(buffer.get(), 5);
   test1 = input.tellg();
-  ComparePrettyPrintToChars(
-      test1, "std::fpos with stream offset:5 with state: {count:0 value:0}");
+  ComparePrettyPrintToRegex(test1, "^std::fpos with stream offset:5( with state: {count:0 value:0})?$");
 }
 
 int main(int, char**) {
diff --git a/libcxx/utils/gdb/libcxx/printers.py b/libcxx/utils/gdb/libcxx/printers.py
index d98b6269f1f9..8d103ad5b399 100644
--- a/libcxx/utils/gdb/libcxx/printers.py
+++ b/libcxx/utils/gdb/libcxx/printers.py
@@ -757,10 +757,18 @@ class StdFposPrinter(object):
         typename = _remove_generics(_prettify_typename(self.val.type))
         offset = self.val["__off_"]
         state = self.val["__st_"]
-        count = state["__count"]
-        value = state["__value"]["__wch"]
-        return "%s with stream offset:%s with state: {count:%s value:%s}" % (
-            typename, offset, count, value)
+
+        state_fields = []
+        if state.type.code == gdb.TYPE_CODE_STRUCT:
+            state_fields = [f.name for f in state.type.fields()]
+
+        state_string = ""
+        if "__count" in state_fields and "__value" in state_fields:
+            count = state["__count"]
+            value = state["__value"]["__wch"]
+            state_string = " with state: {count:%s value:%s}" % (count, value)
+
+        return "%s with stream offset:%s%s" % (typename, offset, state_string)
 
 
 class AbstractUnorderedCollectionPrinter(object):
-- 
2.37.3.968.ga6b4b080e4-goog