Prevent compilers optimizing eval timebomb code out of existence.

The variable that holds the eval license key is a placeholder that is
patched during package installation.  Unfortunately, for a non-final
package build, the placeholder is filled with nulls at compile-time and
a clever compiler will optimize away most of the eval timebomb code due
to a check in the eval code for the first character of the license key
being null.

This commit makes the variable that holds the license key volatile, to
convince compilers that they cannot make assumptions about the contents
of the variable when optimizing.

Task-number: QT-3848
Acked-by: Thiago Macieira

3 files changed, 4 insertions, 4 deletions

diff --git a/configure b/configure
index 5aab180..059aa1a 100755
--- a/configure
+++ b/configure
@@ -4520,7 +4520,7 @@ if [ -n "$EVALKEY" ]; then
     rm -f "$outpath/src/corelib/global/qconfig_eval.cpp"
     cat > "$outpath/src/corelib/global/qconfig_eval.cpp" <<EOF
 /* Evaluation license key */
-static const char qt_eval_key_data                   [512 + 12] = "$EVALKEY";
+static const volatile char qt_eval_key_data                   [512 + 12] = "$EVALKEY";
 EOF
     chmod -w "$outpath/src/corelib/global/qconfig_eval.cpp"
 fi
diff --git a/src/corelib/kernel/qtcore_eval.cpp b/src/corelib/kernel/qtcore_eval.cpp
index 78556c3..da76b74 100644
--- a/src/corelib/kernel/qtcore_eval.cpp
+++ b/src/corelib/kernel/qtcore_eval.cpp
@@ -90,14 +90,14 @@ static const char will_shutdown_now[] =
 
 static int qt_eval_is_supported()
 {
-    const char *const license_key = qt_eval_key_data + 12;
+    const volatile char *const license_key = qt_eval_key_data + 12;
 
     // fast fail
     if (!qt_eval_key_data[0] || !*license_key)
         return -1;
 
     // is this an unsupported evaluation?
-    const char* typecode = license_key;
+    const volatile char *typecode = license_key;
     int field = 2;
     for ( ; field && *typecode; ++typecode)
         if (*typecode == '-')
diff --git a/tools/configure/configureapp.cpp b/tools/configure/configureapp.cpp
index 3808c4e..5966fd2 100644
--- a/tools/configure/configureapp.cpp
+++ b/tools/configure/configureapp.cpp
@@ -3331,7 +3331,7 @@ void Configure::generateConfigfiles()
     if (tmpFile3.open()) {
         tmpStream.setDevice(&tmpFile3);
         tmpStream << "/* Evaluation license key */" << endl
-                  << "static const char qt_eval_key_data              [512 + 12] = \"qt_qevalkey=" << licenseInfo["LICENSEKEYEXT"] << "\";" << endl;
+                  << "static const volatile char qt_eval_key_data              [512 + 12] = \"qt_qevalkey=" << licenseInfo["LICENSEKEYEXT"] << "\";" << endl;
 
         tmpStream.flush();
         tmpFile3.flush();