From e4ed47ef4a7fafbc63febc58d13eca247db64a05 Mon Sep 17 00:00:00 2001
From: Thiago Macieira <thiago.macieira@intel.com>
Date: Fri, 23 Apr 2021 14:44:34 -0700
Subject: [PATCH] QCoreApplication::applicationFilePath: add ELF auxval support

This implements getting the executable file name for FreeBSD. Linux has
a similar functionality (but called AT_EXECFN), but the /proc/self/exe
trick is actually better: it returns a full canonical path instead of
the argument passed to execve(), and it follows a rename of the
executable.

Change-Id: I7a386ad4f0cb4e2ba629fffd16789acda415213f
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
---
 src/corelib/kernel/qcoreapplication.cpp | 27 ++++++++++++++++++++-----
 1 file changed, 22 insertions(+), 5 deletions(-)

diff --git a/src/corelib/kernel/qcoreapplication.cpp b/src/corelib/kernel/qcoreapplication.cpp
index 78d836d4be..947d61a194 100644
--- a/src/corelib/kernel/qcoreapplication.cpp
+++ b/src/corelib/kernel/qcoreapplication.cpp
@@ -1,7 +1,7 @@
 /****************************************************************************
 **
 ** Copyright (C) 2021 The Qt Company Ltd.
-** Copyright (C) 2016 Intel Corporation.
+** Copyright (C) 2021 Intel Corporation.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the QtCore module of the Qt Toolkit.
@@ -109,6 +109,10 @@
 #  include "qcore_unix_p.h"
 #endif
 
+#if __has_include(<sys/auxv.h>)     // Linux and FreeBSD
+#  include <sys/auxv.h>
+#endif
+
 #ifdef Q_OS_VXWORKS
 #  include <taskLib.h>
 #endif
@@ -2288,11 +2292,24 @@ QString QCoreApplication::applicationDirPath()
 #if !defined(Q_OS_WIN) && !defined(Q_OS_DARWIN)     // qcoreapplication_win.cpp or qcoreapplication_mac.cpp
 static QString qAppFileName()
 {
-#  if defined(Q_OS_LINUX) && (!defined(Q_OS_ANDROID) || defined(Q_OS_ANDROID_EMBEDDED))
-    return QFile::decodeName(qt_readlink("/proc/self/exe"));
-#  endif
-
+#  if defined(Q_OS_ANDROID) && !defined(Q_OS_ANDROID_EMBEDDED)
+    // the actual process on Android is the Java VM, so this doesn't help us
     return QString();
+#  elif defined(Q_OS_LINUX)
+    // this includes the Embedded Android builds
+    return QFile::decodeName(qt_readlink("/proc/self/exe"));
+#  elif defined(AT_EXECPATH)
+    // seen on FreeBSD, but I suppose the other BSDs could adopt this API
+    char execfn[PATH_MAX];
+    if (elf_aux_info(AT_EXECPATH, execfn, sizeof(execfn)) != 0)
+        execfn[0] = '\0';
+
+    qsizetype len = qstrlen(execfn);
+    return QFile::decodeName(QByteArray::fromRawData(execfn, len));
+#  else
+    // other OS or something
+    return QString();
+#endif
 }
 #endif