util: Replace non-threadsafe strerror

Some uses of non-threadsafe `strerror` have snuck into the code since
they were removed in #4152. Add a wrapper `SysErrorString` for
thread-safe strerror alternatives and replace all uses of `strerror`
with this.

src/util/sock.cpp

@@ -7,6 +7,7 @@
 #include <threadinterrupt.h>
 #include <tinyformat.h>
 #include <util/sock.h>
+#include <util/syserror.h>
 #include <util/system.h>
 #include <util/time.h>
 
@@ -344,19 +345,8 @@ std::string NetworkErrorString(int err)
 #else
 std::string NetworkErrorString(int err)
 {
-    char buf[256];
-    buf[0] = 0;
-    /* Too bad there are two incompatible implementations of the
-     * thread-safe strerror. */
-    const char *s;
-#ifdef STRERROR_R_CHAR_P /* GNU variant can return a pointer outside the passed buffer */
-    s = strerror_r(err, buf, sizeof(buf));
-#else /* POSIX variant always returns message in buffer */
-    s = buf;
-    if (strerror_r(err, buf, sizeof(buf)))
-        buf[0] = 0;
-#endif
-    return strprintf("%s (%d)", s, err);
+    // On BSD sockets implementations, NetworkErrorString is the same as SysErrorString.
+    return SysErrorString(err);
 }
 #endif
 

src/util/syserror.cpp

@@ -0,0 +1,29 @@
+// Copyright (c) 2020-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#if defined(HAVE_CONFIG_H)
+#include <config/bitcoin-config.h>
+#endif
+
+#include <tinyformat.h>
+#include <util/syserror.h>
+
+#include <cstring>
+
+std::string SysErrorString(int err)
+{
+    char buf[256];
+    buf[0] = 0;
+    /* Too bad there are two incompatible implementations of the
+     * thread-safe strerror. */
+    const char *s;
+#ifdef STRERROR_R_CHAR_P /* GNU variant can return a pointer outside the passed buffer */
+    s = strerror_r(err, buf, sizeof(buf));
+#else /* POSIX variant always returns message in buffer */
+    s = buf;
+    if (strerror_r(err, buf, sizeof(buf)))
+        buf[0] = 0;
+#endif
+    return strprintf("%s (%d)", s, err);
+}

src/util/syserror.h

@@ -0,0 +1,16 @@
+// Copyright (c) 2010-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_UTIL_SYSERROR_H
+#define BITCOIN_UTIL_SYSERROR_H
+
+#include <string>
+
+/** Return system error string from errno value. Use this instead of
+ * std::strerror, which is not thread-safe. For network errors use
+ * NetworkErrorString from sock.h instead.
+ */
+std::string SysErrorString(int err);
+
+#endif // BITCOIN_UTIL_SYSERROR_H

src/util/system.cpp

@@ -25,6 +25,7 @@
 #include <util/getuniquepath.h>
 #include <util/strencodings.h>
 #include <util/string.h>
+#include <util/syserror.h>
 #include <util/translation.h>
 
 
@@ -1374,7 +1375,7 @@ void ScheduleBatchPriority()
     const static sched_param param{};
     const int rc = pthread_setschedparam(pthread_self(), SCHED_BATCH, &param);
     if (rc != 0) {
-        LogPrintf("Failed to pthread_setschedparam: %s\n", strerror(rc));
+        LogPrintf("Failed to pthread_setschedparam: %s\n", SysErrorString(rc));
     }
 #endif
 }