QCryptographicHash: auto-calculate MaxHashLength

Add Algorithm::NumAlgorithms and use it to iterate over all
statically-available algorithms, querying their hashLengthInternal().

This avoids having to statically_assert(<= MaxHashLength) everywhere,
and auto-adjusts the buffer size in SHA1_ONLY builds.

Yes, the extra case labels for NumAlgorithms are a nuisance, but at
least the compiler will remind us when we forget, unlike a missing
static_cast(<= MaxHashLength) that might easily be forgotten.

Adjust the test (which iterates over the QMetaEnum for
QCryptographicHash::Algorithm, so finds NumAlgorithms and tries to
pass it to the hash() function which responds with a
Q_UNREACHABLE(). Only test hashLength() == 0 for that enum value.

Pick-to: 6.5
Change-Id: I70155d2460464f0b2094e136eb6bea185effc9d5
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 9 insertions, 2 deletions

diff --git a/tests/auto/corelib/tools/qcryptographichash/tst_qcryptographichash.cpp b/tests/auto/corelib/tools/qcryptographichash/tst_qcryptographichash.cpp
index 00f7afc876..4ac176fea1 100644
--- a/tests/auto/corelib/tools/qcryptographichash/tst_qcryptographichash.cpp
+++ b/tests/auto/corelib/tools/qcryptographichash/tst_qcryptographichash.cpp
@@ -401,8 +401,15 @@ void tst_QCryptographicHash::hashLength()
 {
     QFETCH(const QCryptographicHash::Algorithm, algorithm);
 
-    QByteArray output = QCryptographicHash::hash("test", algorithm);
-    QCOMPARE(QCryptographicHash::hashLength(algorithm), output.size());
+    qsizetype expectedSize;
+    if (algorithm == QCryptographicHash::NumAlgorithms) {
+        // It's UB to call ::hash() with NumAlgorithms, but hashLength() is
+        // fine and returns 0 for invalid values:
+        expectedSize = 0;
+    } else {
+        expectedSize = QCryptographicHash::hash("test", algorithm).size();
+    }
+    QCOMPARE(QCryptographicHash::hashLength(algorithm), expectedSize);
 }
 
 void tst_QCryptographicHash::move()