add $$num_add() (numeric addition) function

amazing how we managed to do without it for so long. ^^

the name is intentionally somewhat obscure to avoid clashes, and some
namespacing is good anyway.

[ChangeLog][qmake] Added $$num_add() function.

Change-Id: Ib7648b1f425ef096a87b51f158d0f1409e5c4daa
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>
Reviewed-by: Lars Knoll <lars.knoll@theqtcompany.com>
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>

qmake/doc/src/qmake-manual.qdoc

@@ -2943,6 +2943,27 @@
     \c position defaults to 0, causing the first value in the list to be
     returned.
 
+    \section2 num_add(arg1 [, arg2 ..., argn])
+
+    Takes an arbitrary number of numeric arguments and adds them up,
+    returning the sum.
+
+    Subtraction is implicitly supported due to the possibility to simply
+    prepend a minus sign to a numeric value to negate it:
+
+    \code
+    sum = $$num_add($$first, -$$second)
+    \endcode
+
+    If the operand may be already negative, another step is necessary to
+    normalize the number:
+
+    \code
+    second_neg = -$$second
+    second_neg ~= s/^--//
+    sum = $$num_add($$first, $$second_neg)
+    \endcode
+
     \section2 prompt(question)
 
     Displays the specified \c question, and returns a value read from stdin.

qmake/library/qmakebuiltins.cpp

@@ -81,8 +81,8 @@ QT_BEGIN_NAMESPACE
 
 enum ExpandFunc {
     E_INVALID = 0, E_MEMBER, E_FIRST, E_TAKE_FIRST, E_LAST, E_TAKE_LAST, E_SIZE,
-    E_CAT, E_FROMFILE, E_EVAL, E_LIST,
+    E_CAT, E_FROMFILE, E_EVAL, E_LIST, E_SPRINTF, E_FORMAT_NUMBER,
-    E_SPRINTF, E_FORMAT_NUMBER, E_JOIN, E_SPLIT, E_BASENAME, E_DIRNAME, E_SECTION,
+    E_NUM_ADD, E_JOIN, E_SPLIT, E_BASENAME, E_DIRNAME, E_SECTION,
     E_FIND, E_SYSTEM, E_UNIQUE, E_REVERSE, E_QUOTE, E_ESCAPE_EXPAND,
     E_UPPER, E_LOWER, E_TITLE, E_FILES, E_PROMPT, E_RE_ESCAPE, E_VAL_ESCAPE,
     E_REPLACE, E_SORT_DEPENDS, E_RESOLVE_DEPENDS, E_ENUMERATE_VARS,
@@ -116,6 +116,7 @@ void QMakeEvaluator::initFunctionStatics()
         { "list", E_LIST },
         { "sprintf", E_SPRINTF },
         { "format_number", E_FORMAT_NUMBER },
+        { "num_add", E_NUM_ADD },
         { "join", E_JOIN },
         { "split", E_SPLIT },
         { "basename", E_BASENAME },
@@ -594,6 +595,29 @@ ProStringList QMakeEvaluator::evaluateBuiltinExpand(
         }
       formfail:
         break;
+    case E_NUM_ADD:
+        if (args.count() < 1 || args.at(0).isEmpty()) {
+            evalError(fL1S("num_add(num, ...) requires at least one argument."));
+        } else {
+            qlonglong sum = 0;
+            for (const ProString &arg : qAsConst(args)) {
+                if (arg.contains(QLatin1Char('.'))) {
+                    evalError(fL1S("num_add(): floats are currently not supported."));
+                    goto nafail;
+                }
+                bool ok;
+                qlonglong num = arg.toLongLong(&ok);
+                if (!ok) {
+                    evalError(fL1S("num_add(): malformed number %1.")
+                              .arg(arg.toQString(m_tmp3)));
+                    goto nafail;
+                }
+                sum += num;
+            }
+            ret += ProString(QString::number(sum));
+        }
+      nafail:
+        break;
     case E_JOIN: {
         if (args.count() < 1 || args.count() > 4) {
             evalError(fL1S("join(var, glue, before, after) requires one to four arguments."));

tests/auto/tools/qmakelib/evaltest.cpp

@@ -954,6 +954,48 @@ void tst_qmakelib::addReplaceFunctions(const QString &qindir)
             << "##:1: format_number(): invalid format option foo=bar."
             << true;
 
+    QTest::newRow("$$num_add(): one")
+            << "VAR = $$num_add(10)"
+            << "VAR = 10"
+            << ""
+            << true;
+
+    QTest::newRow("$$num_add(): two")
+            << "VAR = $$num_add(1, 2)"
+            << "VAR = 3"
+            << ""
+            << true;
+
+    QTest::newRow("$$num_add(): three")
+            << "VAR = $$num_add(1, 3, 5)"
+            << "VAR = 9"
+            << ""
+            << true;
+
+    QTest::newRow("$$num_add(): negative")
+            << "VAR = $$num_add(7, -13)"
+            << "VAR = -6"
+            << ""
+            << true;
+
+    QTest::newRow("$$num_add(): bad number of arguments")
+            << "VAR = $$num_add()"
+            << "VAR = "
+            << "##:1: num_add(num, ...) requires at least one argument."
+            << true;
+
+    QTest::newRow("$$num_add(): bad number: float")
+            << "VAR = $$num_add(1.1)"
+            << "VAR ="
+            << "##:1: num_add(): floats are currently not supported."
+            << true;
+
+    QTest::newRow("$$num_add(): bad number: malformed")
+            << "VAR = $$num_add(fail)"
+            << "VAR ="
+            << "##:1: num_add(): malformed number fail."
+            << true;
+
     QTest::newRow("$$join(): empty")
             << "IN = \nVAR = $$join(IN, //)"
             << "VAR ="