From f616975e28d6bcae3c5364da5c3ea7ae4f80809c Mon Sep 17 00:00:00 2001
From: Alessio Quaglino <quaglino@google.com>
Date: Fri, 31 May 2024 01:17:08 -0700
Subject: [PATCH] Forward fix for MJCF parsing: A recent libc++ update does not
 natively accept ".x"  float format ('.' being the first character) but rather
 requires "0.x".

PiperOrigin-RevId: 638946382
Change-Id: I3ccb1b5fedc6749a3459916b41148629933fb8c4
---
 src/xml/xml_util.cc | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/xml/xml_util.cc b/src/xml/xml_util.cc
index eec0dd39..651e3586 100644
--- a/src/xml/xml_util.cc
+++ b/src/xml/xml_util.cc
@@ -481,6 +481,16 @@ bool mjXUtil::ReadAttrValues(XMLElement* elem, const char* attr,
   // read numbers
   for (int i = 0; (max < 0 || i < max) && !strm.eof(); ++i) {
     strm >> token;
+
+    // some C++ libraries do not allow .x instead of 0.x
+    if (!token.empty()) {
+      if (token[0] == std::string(".")[0]) {
+        token = "0" + token;
+      } else if (token[0] == std::string("-")[0] && token[1] == std::string(".")[0]) {
+        token.insert(1, "0");
+      }
+    }
+
     std::istringstream token_strm(token);
     token_strm >> item;
     if (token_strm.fail() || !token_strm.eof()) {