Fix Crash when Python is not Found on Windows (#6870)

* check for process failure in python version check

* unify windows and linux python checks

* add mac python advice to translation strings

* remove unnecessary QProcess includes

* import sys in 64-bit python check

* fix indentation

* fix crash on invalid command

* Revert "remove unnecessary QProcess includes" (moved to another pr)

This reverts commit 31f04ea.

* try removing unusedPrivateFunction cppcheck suppression

* undo if/ifdef reorder

* add else comment

* Revert "fix crash on invalid command"

I forgot that this only becomes necessary when some other changes are
added (which will come in another PR)

This reverts commit 15982ce.

* formatting

* remove newline

* update changelog

* wording

Author: CoolSpy3

docs/reference/changelog-r2025.md

@@ -18,6 +18,7 @@
     - Fixed a bug causing `TrackWheel` nodes to lose their field values when used in a proto converted to a base node ([#6856](https://github.com/cyberbotics/webots/pull/6856)).
     - Fixed a bug causing supervisors to occasionally read stale field values after the simulation was reset ([#6758](https://github.com/cyberbotics/webots/pull/6758)).
     - Fixed a bug causing Webots to occasionally crash when unloading a world ([#6857](https://github.com/cyberbotics/webots/pull/6857)).
+    - Fixed a crash occurring when Python was not found on Windows ([#6870](https://github.com/cyberbotics/webots/pull/6870)).
 
 ## Webots R2025a
 Released on January 31st, 2025.

src/webots/control/WbLanguageTools.cpp

@@ -67,44 +67,25 @@ QString WbLanguageTools::pythonCommand(QString &shortVersion, const QString &com
   if (pythonCommand.isEmpty())
 #ifdef _WIN32
     pythonCommand = "python";
+  if (!command.endsWith(".exe", Qt::CaseInsensitive))
+    pythonCommand += ".exe";
 #else
     pythonCommand = "python3";
 #endif
+
   const QString advice =
 #ifdef __APPLE__
-    "To fix the problem, you should set the full path of your python command in "
-    "Webots->preferences->python command.\n";
+    QObject::tr("To fix the problem, you should set the full path of your python command in "
+                "Webots->preferences->python command.\n");
 #else
     QObject::tr("Webots requires Python version 3.7 or newer in your current PATH.\n"
                 "To fix the problem, you should:\n"
                 "1. Check the Python command set in the Webots preferences.\n"
                 "2. Check the COMMAND set in the [python] section of the runtime.ini file of your controller program if any.\n"
                 "3. Install a recent Python 64 bit version and ensure your PATH environment variable points to it.\n");
 #endif
-#ifdef _WIN32
-  if (!command.endsWith(".exe", Qt::CaseInsensitive))
-    pythonCommand += ".exe";
-  QProcess process;
-  process.setProcessEnvironment(env);
-  process.start(pythonCommand, QStringList() << "-u"
-                                             << "-c"
-                                             << "import sys;print(sys.version);print(sys.maxsize > 2**32)");
-  process.waitForFinished();
-  const QString output = process.readAll();
-  // "3.6.3 (v3.6.3:2c5fed8, Oct  3 2017, 18:11:49) [MSC v.1900 64 bit (AMD64)]\nTrue\n" or the like
-  const QStringList version = output.split("\n");
-  const int v = (QString(version[0][2]) + (version[0][3] != '.' ? QString(version[0][3]) : "")).toInt();
-  if (!version[0].startsWith("3.") || v < 7) {
-    WbLog::warning(QObject::tr("\"%1\" was not found.\n").arg(pythonCommand) + advice);
-    pythonCommand = "!";
-  } else if (version.size() > 1 && version[1].startsWith("False")) {
-    WbLog::warning(QObject::tr("\"%1\" 64 bit was not found, but the 32 bit version was found.\n").arg(pythonCommand) + advice);
-    pythonCommand = "!";
-  } else
-    shortVersion = QString(version[0][0]) + version[0][2];
-  if (version[0][3] != '.')
-    shortVersion += version[0][3];  // handle versions 310, 311, 321, etc.
-#elif __APPLE__
+
+#ifdef __APPLE__
   if (std::getenv("PWD"))
     shortVersion = checkIfPythonCommandExist(pythonCommand, env, true);
   else if (pythonCommand == "python" || pythonCommand == "python3") {
@@ -129,39 +110,58 @@ QString WbLanguageTools::pythonCommand(QString &shortVersion, const QString &com
 
   if (pythonCommand == "!")
     WbLog::warning(QObject::tr("Python was not found.\n") + advice);
-#else  // __linux__
-      shortVersion = checkIfPythonCommandExist(pythonCommand, env, true);
+#else  // __linux__ and _WIN32
+  shortVersion = checkIfPythonCommandExist(pythonCommand, env, true);
   if (shortVersion.isEmpty()) {
     pythonCommand = "!";
     WbLog::warning(QObject::tr("Python was not found.\n") + advice);
+  } else {  // Python exists
+
+#ifdef _WIN32  // 64-bit check
+    QProcess process;
+    process.setProcessEnvironment(env);
+    process.start(pythonCommand, QStringList() << "-u"
+                                               << "-c"
+                                               << "import sys;print(sys.maxsize > 2**32)");
+    process.waitForFinished();
+    bool processSucceeded = process.error() == QProcess::UnknownError;
+    const QString output = process.readAll();
+    if (!processSucceeded || !output.startsWith("True")) {
+      WbLog::warning(QObject::tr("\"%1\" 64 bit was not found, but the 32 bit version was found.\n").arg(pythonCommand) +
+                     advice);
+      pythonCommand = "!";
+      shortVersion = QString();
+    }
+#endif         // _WIN32
   }
 
-#endif
+#endif  // __APPLE__
+
   return pythonCommand;
 }
 
-#if defined __APPLE__ || defined __linux__
 const QString WbLanguageTools::checkIfPythonCommandExist(const QString &pythonCommand, QProcessEnvironment &env, bool log) {
   QString shortVersion;
   QProcess process;
   process.setProcessEnvironment(env);
   process.start(pythonCommand, QStringList() << "-c"
                                              << "import sys;print(sys.version);");
   process.waitForFinished();
+  bool processSucceeded = process.error() == QProcess::UnknownError;
   const QString output = process.readAll();
   // "3.8.10 (tags/v3.8.10:3d8993a, May  3 2021, 11:48:03) [MSC v.1928 64 bit (AMD64)]" or the like
   const QStringList version = output.split(" ");
-  if (!version[0].startsWith("3.")) {
+  const QStringList version_numbers(version[0].split("."));
+  const int minor_version = version_numbers.size() >= 2 ? version_numbers[1].toInt() : 0;
+  if (!processSucceeded || !version[0].startsWith("3.") || minor_version < 7) {
     if (log)
       WbLog::warning(QObject::tr("\"%1\" was not found.\n").arg(pythonCommand));
     shortVersion = QString();
   } else {
-    const QStringList version_numbers(version[0].split("."));
     shortVersion = version_numbers[0] + version_numbers[1];
   }
   return shortVersion;
 }
-#endif
 
 #ifdef __APPLE__
 QString WbLanguageTools::findWorkingPythonPath(const QString &pythonVersion, QProcessEnvironment &env, bool log) {

src/webots/control/WbLanguageTools.hpp

@@ -35,10 +35,7 @@ class WbLanguageTools {
 private:
   WbLanguageTools() {}
   ~WbLanguageTools() {}
-#if defined __APPLE__ || defined __linux__
-  // cppcheck-suppress unusedPrivateFunction
   static const QString checkIfPythonCommandExist(const QString &pythonCommand, QProcessEnvironment &env, bool log);
-#endif
 #ifdef __APPLE__
   static QString findWorkingPythonPath(const QString &pythonVersion, QProcessEnvironment &env, bool log);
 #endif