PitchShiftEffect: add id literals into a namespace

This commits creates literal constants in the anonymous namespace.
The constants values are the same as the manifest
parameter identifiers. The constants are created to avoid grammar bugs
due to the value has to be used twice on the other code places. Due to
the literal being used, the segmentation fault has occurred
without previous warnings or errors if the entered identifier names
for the specific parameter are not the same.

src/effects/backends/builtin/pitchshifteffect.cpp

@@ -1,9 +1,16 @@
 #include "effects/backends/builtin/pitchshifteffect.h"
 
+#include <QString>
+
 #include "util/sample.h"
 
 namespace {
 static constexpr SINT kSemitonesPerOctave = 12;
+
+static const QString kPitchParameterId = QStringLiteral("pitch");
+static const QString kRangeParameterId = QStringLiteral("range");
+static const QString kSemitonesModeParameterId = QStringLiteral("semitonesMode");
+static const QString kFormantPreservingParameterId = QStringLiteral("formantPreserving");
 } // anonymous namespace
 
 PitchShiftEffect::PitchShiftEffect()
@@ -59,7 +66,7 @@ EffectManifestPointer PitchShiftEffect::getManifest() {
             "Raises or lowers the original pitch of a sound."));
 
     EffectManifestParameterPointer pitch = pManifest->addParameter();
-    pitch->setId("pitch");
+    pitch->setId(kPitchParameterId);
     pitch->setName(QObject::tr("Pitch"));
     pitch->setShortName(QObject::tr("Pitch"));
     pitch->setDescription(QObject::tr(
@@ -70,7 +77,7 @@ EffectManifestPointer PitchShiftEffect::getManifest() {
     pitch->setRange(-1.0, 0.0, 1.0);
 
     EffectManifestParameterPointer range = pManifest->addParameter();
-    range->setId("range");
+    range->setId(kRangeParameterId);
     range->setName(QObject::tr("Range"));
     range->setShortName(QObject::tr("Range"));
     range->setDescription(QObject::tr(
@@ -81,7 +88,7 @@ EffectManifestPointer PitchShiftEffect::getManifest() {
     range->setRange(0.0, 1.0, 2.0);
 
     EffectManifestParameterPointer semitonesMode = pManifest->addParameter();
-    semitonesMode->setId("semitonesMode");
+    semitonesMode->setId(kSemitonesModeParameterId);
     semitonesMode->setName(QObject::tr("Semitones"));
     semitonesMode->setShortName(QObject::tr("Semitones"));
     semitonesMode->setDescription(QObject::tr(
@@ -91,7 +98,7 @@ EffectManifestPointer PitchShiftEffect::getManifest() {
     semitonesMode->setRange(0, 1, 1);
 
     EffectManifestParameterPointer formantPreserving = pManifest->addParameter();
-    formantPreserving->setId("formantPreserving");
+    formantPreserving->setId(kFormantPreservingParameterId);
     formantPreserving->setName(QObject::tr("Formant"));
     formantPreserving->setShortName(QObject::tr("Formant"));
     formantPreserving->setDescription(QObject::tr(
@@ -107,10 +114,10 @@ EffectManifestPointer PitchShiftEffect::getManifest() {
 
 void PitchShiftEffect::loadEngineEffectParameters(
         const QMap<QString, EngineEffectParameterPointer>& parameters) {
-    m_pPitchParameter = parameters.value("pitch");
-    m_pRangeParameter = parameters.value("range");
-    m_pSemitonesModeParameter = parameters.value("semitonesMode");
-    m_pFormantPreservingParameter = parameters.value("formantPreserving");
+    m_pPitchParameter = parameters.value(kPitchParameterId);
+    m_pRangeParameter = parameters.value(kRangeParameterId);
+    m_pSemitonesModeParameter = parameters.value(kSemitonesModeParameterId);
+    m_pFormantPreservingParameter = parameters.value(kFormantPreservingParameterId);
 }
 
 void PitchShiftEffect::processChannel(