Make sure $$relative_path() uses an absolute path as its first arg

Thanks to QTBUG-61373, this qmake function was called with
/usr/local/5.10.1 as baseDir, which isn't absolute, leading to an
assertion failure.  We could raise the error within qmake but it
proved easier to simply resolve any non-absolute baseDir using PWD,
before trying to use it as an absolute path.

Did the same for $$absolute_path().  Documented both.  Adjusted the
assert that caught this to report any non-absolute path that upsets
it.  Added simple tests, fixed an existing test.

Task-number: QTBUG-66156
Change-Id: Icfef2e2f5b236e071177c9beffa38d71bf404292
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>

3 files changed, 18 insertions, 7 deletions

diff --git a/qmake/doc/src/qmake-manual.qdoc b/qmake/doc/src/qmake-manual.qdoc
index cc3b73418b..35f24e1793 100644
--- a/qmake/doc/src/qmake-manual.qdoc
+++ b/qmake/doc/src/qmake-manual.qdoc
@@ -2913,7 +2913,8 @@
     Returns the absolute path of \c path.
 
     If \c base is not specified, uses the current directory as the base
-    directory.
+    directory.  If it is a relative path, it is resolved relative to the current
+    directory before use.
 
     For example, the following call returns the string
     \c {"/home/johndoe/myproject/readme.txt"}:
@@ -3152,9 +3153,15 @@
 
     \section2 relative_path(filePath[, base])
 
-    Returns the path to \c filePath relative to \c base. If \c base is not
-    specified, it is the current project directory. This function is a wrapper
-    around QDir::relativeFilePath.
+    Returns the path to \c filePath relative to \c base.
+
+    If \c base is not specified, it is the current project
+    directory. If it is relative, it is resolved relative to the
+    current project directory before use.
+
+    If \c filePath is relative, it is first resolved against the base
+    directory; in that case, this function effectively acts as
+    $$clean_path().
 
     See also \l{absolute_path(path[, base])}{absolute_path()},
     \l{clean_path(path)}{clean_path()}.
diff --git a/qmake/library/ioutils.cpp b/qmake/library/ioutils.cpp
index afd41912fe..cb4aa5e74d 100644
--- a/qmake/library/ioutils.cpp
+++ b/qmake/library/ioutils.cpp
@@ -103,7 +103,7 @@ QString IoUtils::resolvePath(const QString &baseDir, const QString &fileName)
         return QDir::cleanPath(fileName);
 #ifdef Q_OS_WIN // Add drive to otherwise-absolute path:
     if (fileName.at(0).unicode() == '/' || fileName.at(0).unicode() == '\\') {
-        Q_ASSERT(isAbsolutePath(baseDir));
+        Q_ASSERT_X(isAbsolutePath(baseDir), "IoUtils::resolvePath", qUtf8Printable(baseDir));
         return QDir::cleanPath(baseDir.left(2) + fileName);
     }
 #endif // Q_OS_WIN
diff --git a/qmake/library/qmakebuiltins.cpp b/qmake/library/qmakebuiltins.cpp
index 83c3d1d643..0a83b9b930 100644
--- a/qmake/library/qmakebuiltins.cpp
+++ b/qmake/library/qmakebuiltins.cpp
@@ -1178,7 +1178,9 @@ QMakeEvaluator::VisitReturn QMakeEvaluator::evaluateBuiltinExpand(
             evalError(fL1S("absolute_path(path[, base]) requires one or two arguments."));
         } else {
             QString arg = args.at(0).toQString(m_tmp1);
-            QString baseDir = args.count() > 1 ? args.at(1).toQString(m_tmp2) : currentDirectory();
+            QString baseDir = args.count() > 1
+                    ? IoUtils::resolvePath(currentDirectory(), args.at(1).toQString(m_tmp2))
+                    : currentDirectory();
             QString rstr = arg.isEmpty() ? baseDir : IoUtils::resolvePath(baseDir, arg);
             ret << (rstr.isSharedWith(m_tmp1)
                         ? args.at(0)
@@ -1192,7 +1194,9 @@ QMakeEvaluator::VisitReturn QMakeEvaluator::evaluateBuiltinExpand(
             evalError(fL1S("relative_path(path[, base]) requires one or two arguments."));
         } else {
             QString arg = args.at(0).toQString(m_tmp1);
-            QString baseDir = args.count() > 1 ? args.at(1).toQString(m_tmp2) : currentDirectory();
+            QString baseDir = args.count() > 1
+                    ? IoUtils::resolvePath(currentDirectory(), args.at(1).toQString(m_tmp2))
+                    : currentDirectory();
             QString absArg = arg.isEmpty() ? baseDir : IoUtils::resolvePath(baseDir, arg);
             QString rstr = QDir(baseDir).relativeFilePath(absArg);
             ret << (rstr.isSharedWith(m_tmp1) ? args.at(0) : ProString(rstr).setSource(args.at(0)));