configure: make C++11 <random> a required functionality

Error out if it's missing or broken (Mersenne Twister not present).

This ensures that we never have a low-quality random generator in Qt.

Change-Id: I0a103569c81b4711a649fffd14ec80649df7087e
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

3 files changed, 12 insertions, 44 deletions

diff --git a/src/corelib/configure.json b/src/corelib/configure.json
index 51e6d1d391..8067ca70f1 100644
--- a/src/corelib/configure.json
+++ b/src/corelib/configure.json
@@ -459,11 +459,6 @@
             "condition": "tests.cxx11_future",
             "output": [ "publicFeature" ]
         },
-        "cxx11_random": {
-            "label": "C++11 <random>",
-            "condition": "tests.cxx11_random",
-            "output": [ "privateFeature" ]
-        },
         "eventfd": {
             "label": "eventfd",
             "condition": "tests.eventfd",
@@ -869,9 +864,9 @@ ensure that the IDEs they use either set QT_LOGGING_TO_CONSOLE to 1
 or are able to read the logged output from journald, syslog or slog2."
         },
         {
-            "type": "warning",
-            "condition": "!config.win32 && !config.darwin && !config.bsd && !features.cxx11_random",
-            "message": "No high-quality PRNG available for QRandomGenerator fallback.\nIf the HW or OS RNG fails, Qt will abort execution."
+            "type": "error",
+            "condition": "!tests.cxx11_random",
+            "message": "C++11 <random> is required and is missing or failed to compile."
         },
         {
             "type": "error",
diff --git a/src/corelib/global/qrandom.cpp b/src/corelib/global/qrandom.cpp
index bafc312b3e..a7696719d1 100644
--- a/src/corelib/global/qrandom.cpp
+++ b/src/corelib/global/qrandom.cpp
@@ -46,16 +46,15 @@
 #include <qthreadstorage.h>
 #include <private/qsimd_p.h>
 
+#include <random>
+
 #include <errno.h>
 
 #if QT_CONFIG(getentropy)
 #  include <sys/random.h>
-#else
-#  if QT_CONFIG(cxx11_random)
-#    include <random>
-#    include "qdeadlinetimer.h"
-#    include "qhashfunctions.h"
-#  endif
+#elif !defined(Q_OS_BSD4) && !defined(Q_OS_WIN)
+#  include "qdeadlinetimer.h"
+#  include "qhashfunctions.h"
 
 #  if QT_CONFIG(getauxval)
 #    include <sys/auxv.h>
@@ -258,7 +257,7 @@ static void fallback_fill(quint32 *ptr, qssize_t left) Q_DECL_NOTHROW
     // BSDs have arc4random(4) and these work even in chroot(2)
     arc4random_buf(ptr, left * sizeof(*ptr));
 }
-#elif QT_CONFIG(cxx11_random)
+#else
 static QBasicAtomicInteger<unsigned> seed = Q_BASIC_ATOMIC_INITIALIZER(0U);
 static void fallback_update_seed(unsigned value)
 {
@@ -343,12 +342,6 @@ static void fallback_fill(quint32 *ptr, qssize_t left) Q_DECL_NOTHROW
 
     fallback_update_seed(*ptr);
 }
-#else
-static void fallback_update_seed(unsigned) {}
-static Q_NORETURN void fallback_fill(quint32 *, qssize_t)
-{
-    qFatal("Random number generator failed and no high-quality backup available");
-}
 #endif
 
 static qssize_t fill_cpu(quint32 *buffer, qssize_t count) Q_DECL_NOTHROW
diff --git a/tests/auto/corelib/global/qrandomgenerator/tst_qrandomgenerator.cpp b/tests/auto/corelib/global/qrandomgenerator/tst_qrandomgenerator.cpp
index bf43f6d710..2195bf8ec8 100644
--- a/tests/auto/corelib/global/qrandomgenerator/tst_qrandomgenerator.cpp
+++ b/tests/auto/corelib/global/qrandomgenerator/tst_qrandomgenerator.cpp
@@ -34,11 +34,9 @@
 #include <private/qrandom_p.h>
 
 #include <algorithm>
-#if QT_CONFIG(cxx11_random)
-#  include <random>
-#endif
+#include <random>
 
-#if !QT_CONFIG(getentropy) && (QT_CONFIG(cxx11_random) || defined(Q_OS_BSD4) || defined(Q_OS_WIN))
+#if !QT_CONFIG(getentropy) && (defined(Q_OS_BSD4) || defined(Q_OS_WIN))
 #  define HAVE_FALLBACK_ENGINE
 #endif
 
@@ -468,9 +466,6 @@ template <typename Engine> void seedStdRandomEngine()
 
 void tst_QRandomGenerator::seedStdRandomEngines()
 {
-#if !QT_CONFIG(cxx11_random)
-    QSKIP("<random> not found");
-#else
     seedStdRandomEngine<std::default_random_engine>();
     seedStdRandomEngine<std::minstd_rand0>();
     seedStdRandomEngine<std::minstd_rand>();
@@ -480,7 +475,6 @@ void tst_QRandomGenerator::seedStdRandomEngines()
     seedStdRandomEngine<std::ranlux48_base>();
     seedStdRandomEngine<std::ranlux24>();
     seedStdRandomEngine<std::ranlux48>();
-#endif
 }
 
 void tst_QRandomGenerator::stdUniformIntDistribution_data()
@@ -511,9 +505,6 @@ void tst_QRandomGenerator::stdUniformIntDistribution_data()
 
 void tst_QRandomGenerator::stdUniformIntDistribution()
 {
-#if !QT_CONFIG(cxx11_random)
-    QSKIP("<random> not found");
-#else
     QFETCH(uint, control);
     QFETCH(quint32, max);
     setRNGControl(control & (SkipHWRNG|SkipSystemRNG|SkipMemfill));
@@ -575,14 +566,11 @@ void tst_QRandomGenerator::stdUniformIntDistribution()
             QVERIFY(value <= dist.max());
         }
     }
-#endif
 }
 
 void tst_QRandomGenerator::stdGenerateCanonical()
 {
-#if !QT_CONFIG(cxx11_random)
-    QSKIP("<random> not found");
-#elif defined(Q_CC_MSVC) && Q_CC_MSVC < 1900
+#if defined(Q_CC_MSVC) && Q_CC_MSVC < 1900
     // see https://connect.microsoft.com/VisualStudio/feedback/details/811611
     QSKIP("MSVC 2013's std::generate_canonical is broken");
 #else
@@ -634,9 +622,6 @@ void tst_QRandomGenerator::stdUniformRealDistribution_data()
 
 void tst_QRandomGenerator::stdUniformRealDistribution()
 {
-#if !QT_CONFIG(cxx11_random)
-    QSKIP("<random> not found");
-#else
     QFETCH(uint, control);
     QFETCH(double, min);
     QFETCH(double, sup);
@@ -663,14 +648,10 @@ void tst_QRandomGenerator::stdUniformRealDistribution()
                 QVERIFY(value < dist.max());
         }
     }
-#endif
 }
 
 void tst_QRandomGenerator::stdRandomDistributions()
 {
-#if !QT_CONFIG(cxx11_random)
-    QSKIP("<random> not found");
-#else
     // just a compile check for some of the distributions, besides
     // std::uniform_int_distribution and std::uniform_real_distribution (tested
     // above)
@@ -695,7 +676,6 @@ void tst_QRandomGenerator::stdRandomDistributions()
         QVERIFY(discrete(rd) != 0);
         QVERIFY_3TIMES(discrete(rd) == 3);
     }
-#endif
 }
 
 QTEST_APPLESS_MAIN(tst_QRandomGenerator)