STYLE: Replace non-POD string constants with constexpr QLatin1String by hjmjohnson · Pull Request #1410 · commontk/CTK

hjmjohnson · 2026-04-02T16:34:09Z

Summary

Fixes clazy:non-pod-global-static warnings on file-scope and class-static string constants by converting them to static constexpr QLatin1String.

This is one of two PRs split from a combined approach (the companion PR #1409 handles ctkLogger globals via Q_GLOBAL_STATIC_WITH_ARGS).

Problem

static QString at file scope or as class static members have non-trivial constructors and destructors, triggering the non-pod-global-static clazy warning. These are subject to the Static Initialization Order Fiasco (SIOF) and add unnecessary startup/teardown overhead.

Approach

QLatin1String is a lightweight wrapper around a const char* + length — no heap allocation, trivially constructible/destructible. All affected constants are pure compile-time string literals, making them ideal constexpr candidates.

Qt5 / Apple-clang compatibility: QLatin1String(const char*) calls strlen(), which Apple clang does not treat as constexpr. The 2-argument constructor with sizeof("literal") - 1 is used instead:

// Before (triggers non-pod-global-static):
static QString PREFIX_EXECUTABLE = "executable:";

// After (zero runtime overhead, compile-time constant):
static constexpr QLatin1String PREFIX_EXECUTABLE{
    "executable:", static_cast<int>(sizeof("executable:") - 1)};

For class static members (ctkPluginFrameworkDebug), the constexpr definition moves entirely into the header (C++17 static constexpr is implicitly inline), the out-of-line QString definitions in the .cpp are removed, and the CTK_OSGI intermediate variable becomes unnecessary:

// Before — header declaration + .cpp definition built from a runtime prefix:
// ctkPluginFrameworkDebug_p.h:  static QString OPTION_DEBUG_GENERAL;
// ctkPluginFrameworkDebug.cpp:  QString ctkPluginFrameworkDebug::OPTION_DEBUG_GENERAL = CTK_OSGI + "/debug";

// After — header-only compile-time constant:
static constexpr QLatin1String OPTION_DEBUG_GENERAL{
    "org.commontk.pluginfw/debug",
    static_cast<int>(sizeof("org.commontk.pluginfw/debug") - 1)};

No call-site changes required — QLatin1String implicitly converts to QString for all existing uses.

Files Changed

File	Change
`Libs/CommandLineModules/Frontend/QtGui/ctkCmdLineModuleObjectTreeWalker.cpp`	4 prefix constants
`Libs/PluginFramework/ctkBasicLocation.cpp`	2 constants
`Libs/PluginFramework/ctkLocationManager.cpp`	11 constants
`Libs/PluginFramework/ctkPluginFrameworkDebug_p.h`	10 class static members → `constexpr` inline
`Libs/PluginFramework/ctkPluginFrameworkDebug.cpp`	Remove 10 out-of-line definitions + `CTK_OSGI` variable
`Libs/PluginFramework/ctkPluginFrameworkLauncher.cpp`	1 constant

Comparison with PR #1398

Aspect	PR #1398	This PR
String constants	Meyers' singleton `const T& name()`	`constexpr QLatin1String name`
Call sites	Need `()` suffix	No change
Runtime overhead	Thread-safe guard on each access	None (compile-time const)
SIOF risk	Eliminated	Eliminated

Testing

Built successfully against Qt5 (cmake-build-clazy-qt5, Apple clang) and Qt6 (cmake-build-clazy-qt6) on macOS ARM64.

Part of the fix for #1407. See also companion PR #1409 for Q_GLOBAL_STATIC_WITH_ARGS logger fixes, and draft PR #1411 for the ctkDICOMModalities API deprecation strategy.

🤖 Generated with Claude Code

Static QString variables have non-trivial constructors and destructors, triggering clazy:non-pod-global-static and introducing Static Initialization Order Fiasco (SIOF) risk. All affected constants are pure compile-time string literals convertible to constexpr QLatin1String. Qt5 / Apple-clang compatibility: QLatin1String(const char*) calls strlen(), which is not constexpr under Apple clang. A local make_constexpr_QLatin1String_ helper in each anonymous namespace deduces the string length at compile time via a const-array-reference parameter, avoiding sizeof/static_cast repetition at every definition site: template<std::size_t N> constexpr QLatin1String make_constexpr_QLatin1String_(const char (&str)[N]) { return QLatin1String{str, static_cast<int>(N - 1)}; } The redundant 'static' specifier is omitted on all anonymous-namespace members (internal linkage is already implied by the enclosing namespace). For ctkPluginFrameworkDebug, the ten OPTION_DEBUG_* class static members are converted to inline static constexpr in the private header using the helper and a #define CTK_OSGI prefix macro (scoped with #undef); the out-of-line QString definitions and CTK_OSGI QString variable are removed from the .cpp entirely. No call-site changes are required -- QLatin1String implicitly converts to QString for all existing uses. Files changed: - Libs/CommandLineModules/Frontend/QtGui/ctkCmdLineModuleObjectTreeWalker.cpp - Libs/PluginFramework/ctkBasicLocation.cpp - Libs/PluginFramework/ctkLocationManager.cpp - Libs/PluginFramework/ctkPluginFrameworkDebug_p.h - Libs/PluginFramework/ctkPluginFrameworkDebug.cpp - Libs/PluginFramework/ctkPluginFrameworkLauncher.cpp Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

hjmjohnson · 2026-04-03T13:37:15Z

CTK Validation Report for PR #1410

Date: 2026-04-03T13:37:14Z
Platform: Linux 6.17.0-1012-oem x86_64

Role	CTK Hash	Commit
Proposed	`1e017029`	`1e01702` (HEAD -> pr-1410) STYLE: Replace non-POD string constants with constexpr QLatin1String
Reference	`935c4e04`	`935c4e0` (HEAD) ENH: Add refreshBrowser to the DICOM visual browser

Validation Actions Performed

#	Action	Scope	Qt	Proposed (`1e017029`)	Reference (`935c4e04`)
1	Build	CTK standalone	Qt5	0 errors, 0 warnings	0 errors, 21 warnings
2	Build	CTK standalone	Qt6	0 errors, 0 warnings	2 errors, 3 warnings
3	Test	CTK standalone	Qt5	267/280 passed, 13 failed	255/280 passed, 25 failed
4	Test	CTK standalone	Qt6	245/255 passed, 10 failed	245/255 passed, 10 failed
5	Build	CTK-in-Slicer (clean)	Qt5	0 errors, 187 warnings	0 errors, 187 warnings
6	Build	Slicer inner build	Qt5	0 errors, 0 warnings	0 errors, 0 warnings
7	Test	Slicer inner build	Qt5	661/670 passed, 9 failed	661/670 passed, 9 failed

CTK-in-Slicer Build Detail (classified warnings)

Source	Proposed warnings	Reference warnings
CTK source code	1	1
CTK dependencies	186	186
Slicer (CTK-related)	0	0
Slicer (own code)	0	0

Slicer Test Detail (classified failures)

Category	Proposed (`1e017029`)	Reference (`935c4e04`)
CTK-related failures	0	0
Slicer-own failures	0	0
Total failed	9	9

CTK Test Failures (proposed 1e017029)

Qt5 (13 failures):

	 94 - ctkFontButtonTest (Timeout)                       CTKWidgets
	 96 - ctkLanguageComboBoxTest (Failed)                  CTKWidgets
	144 - ctkWidgetsUtilsTestGrabWidget (Failed)            CTKWidgets
	158 - ctkColorPickerButtonEventTranslatorPlayerTest1 (Timeout) CTKWidgets
	162 - ctkDirectoryButtonEventTranslatorPlayerTest1 (Timeout) CTKWidgets
	166 - ctkFileDialogEventTranslatorPlayerTest1 (Timeout) CTKWidgets
	170 - ctkMenuComboBoxEventTranslatorPlayerTest1 (Failed) CTKWidgets
	236 - vtkLightBoxRendererManagerTest1 (Subprocess aborted) CTKVisualizationVTKCore
	269 - ctkVTKMagnifyViewTest2OddOdd (Failed)             CTKVisualizationVTKWidgets
	270 - ctkVTKMagnifyViewTest2EvenEven (Failed)           CTKVisualizationVTKWidgets
	271 - ctkVTKMagnifyViewTest2OddEven (Failed)            CTKVisualizationVTKWidgets
	272 - ctkVTKMagnifyViewTest2EvenOdd (Failed)            CTKVisualizationVTKWidgets
	280 - ctkVTKTextPropertyWidgetEventTranslatorPlayerTest1 (Timeout) CTKVisualizationVTKWidgets

Qt6 (10 failures):

	 38 - CTKPluginFrameworkAppTests (Subprocess aborted)   CTKPluginFramework
	 99 - ctkLanguageComboBoxTest (Failed)                  CTKWidgets
	147 - ctkWidgetsUtilsTestGrabWidget (Failed)            CTKWidgets
	148 - ctkWorkflowWidgetTest1 (Failed)                   CTKWidgets
	149 - ctkWorkflowWidgetTest2 (Failed)                   CTKWidgets
	206 - vtkLightBoxRendererManagerTest1 (SEGFAULT)        CTKVisualizationVTKCore
	249 - ctkVTKMagnifyViewTest2OddOdd (Failed)             CTKVisualizationVTKWidgets
	250 - ctkVTKMagnifyViewTest2EvenEven (Failed)           CTKVisualizationVTKWidgets
	251 - ctkVTKMagnifyViewTest2OddEven (Failed)            CTKVisualizationVTKWidgets
	252 - ctkVTKMagnifyViewTest2EvenOdd (Failed)            CTKVisualizationVTKWidgets

CTK Test Failures (reference 935c4e04)

Qt5 (25 failures):

	  7 - ctkBackTraceTest (Failed)                         CTKCore
	 20 - ctkLoggerTest1 (Failed)                           CTKCore
	 94 - ctkFontButtonTest (Timeout)                       CTKWidgets
	 96 - ctkLanguageComboBoxTest (Failed)                  CTKWidgets
	109 - ctkMessageBoxDontShowAgainTest (Failed)           CTKWidgets
	144 - ctkWidgetsUtilsTestGrabWidget (Failed)            CTKWidgets
	158 - ctkColorPickerButtonEventTranslatorPlayerTest1 (Timeout) CTKWidgets
	162 - ctkDirectoryButtonEventTranslatorPlayerTest1 (Failed) CTKWidgets
	166 - ctkFileDialogEventTranslatorPlayerTest1 (Timeout) CTKWidgets
	170 - ctkMenuComboBoxEventTranslatorPlayerTest1 (Failed) CTKWidgets
	173 - ctkPathLineEditEventTranslatorPlayerTest1 (Failed) CTKWidgets
	224 - ctkDICOMPatientDelegateTest1 (Failed)             CTKDICOMWidgets
	236 - vtkLightBoxRendererManagerTest1 (SEGFAULT)        CTKVisualizationVTKCore
	242 - ctkVTKErrorLogModelFileLoggingTest1 (Failed)      CTKVisualizationVTKWidgets
	246 - ctkVTKHistogramTest3 (Failed)                     CTKVisualizationVTKWidgets
	250 - ctkVTKPropertyWidgetTest (Failed)                 CTKVisualizationVTKWidgets
	253 - ctkVTKThresholdWidgetTest1 (Failed)               CTKVisualizationVTKWidgets
	263 - ctkVTKSurfaceMaterialPropertyWidgetTest1 (Failed) CTKVisualizationVTKWidgets
	269 - ctkVTKMagnifyViewTest2OddOdd (Failed)             CTKVisualizationVTKWidgets
	270 - ctkVTKMagnifyViewTest2EvenEven (Failed)           CTKVisualizationVTKWidgets
	271 - ctkVTKMagnifyViewTest2OddEven (Failed)            CTKVisualizationVTKWidgets
	272 - ctkVTKMagnifyViewTest2EvenOdd (Failed)            CTKVisualizationVTKWidgets
	278 - ctkVTKRenderViewEventTranslatorPlayerTest1 (Failed) CTKVisualizationVTKWidgets
	279 - ctkVTKScalarBarWidgetEventTranslatorPlayerTest1 (Failed) CTKVisualizationVTKWidgets
	280 - ctkVTKTextPropertyWidgetEventTranslatorPlayerTest1 (Timeout) CTKVisualizationVTKWidgets

Qt6 (10 failures):

	 38 - CTKPluginFrameworkAppTests (Subprocess aborted)   CTKPluginFramework
	 99 - ctkLanguageComboBoxTest (Failed)                  CTKWidgets
	147 - ctkWidgetsUtilsTestGrabWidget (Failed)            CTKWidgets
	148 - ctkWorkflowWidgetTest1 (Failed)                   CTKWidgets
	149 - ctkWorkflowWidgetTest2 (Failed)                   CTKWidgets
	206 - vtkLightBoxRendererManagerTest1 (SEGFAULT)        CTKVisualizationVTKCore
	249 - ctkVTKMagnifyViewTest2OddOdd (Failed)             CTKVisualizationVTKWidgets
	250 - ctkVTKMagnifyViewTest2EvenEven (Failed)           CTKVisualizationVTKWidgets
	251 - ctkVTKMagnifyViewTest2OddEven (Failed)            CTKVisualizationVTKWidgets
	252 - ctkVTKMagnifyViewTest2EvenOdd (Failed)            CTKVisualizationVTKWidgets

Generated by /validate-ctk-pr skill | cache: /home/johnsonhj/src/CTK/.claude/validate-cache

hjmjohnson · 2026-04-03T13:46:04Z

@jamesobutler I've been developing a method to more completely test each proposed change to CTK.

See the commit message: #1410 (comment).

I built the CTK source code

against Qt5
against Qt6
also used the same CTK code to test in a Slicer Build with Qt5
to verify that no build or test regressions exist. This is the PR that I used to develop the validate-ctk-pr reports.

The report indicates no regressions to tests or builds.

If there are other bits of information you think would be helpful, let me know and I'll try to add them.

lassoan

The proposed syntax and the repetitive utility function is somewhat noisy. According to Claude, there were also some potential ODR violations in ctkPluginFrameworkDebug_p.h.

I've submitted a pull request that describes an alternative solution (I could not push to this branch) - please have a look: #1440

hjmjohnson · 2026-08-30T12:02:47Z

Closing in favor of #1440, which solves the same problem with a cleaner approach.

@lassoan's _L1 user-defined-literal backport (ctkStringLiterals.h) removes the repetitive helper this PR needed for the Qt5/Apple-clang constexpr case, and the static constexpr in-class members resolve the ODR concern he raised on this PR. #1440 covers the same six files, so nothing here is lost by closing it.

Thanks for the review and the alternative.

lassoan · 2026-08-30T16:24:48Z

Thanks! Could you add a review to #1440 (to fulfill the review requirement)?

This was referenced Apr 2, 2026

STYLE: Replace non-POD ctkLogger globals with Q_GLOBAL_STATIC_WITH_ARGS #1409

Open

ENH: Migrate ctkDICOMModalities to ctkDICOMDatabase accessors (stacked on #1418) #1411

Open

hjmjohnson force-pushed the fix-non-pod-constexpr-strings branch 2 times, most recently from 640dab9 to 1e01702 Compare April 2, 2026 17:47

hjmjohnson marked this pull request as draft April 2, 2026 20:34

hjmjohnson mentioned this pull request Apr 3, 2026

COMP: Update CTK to latest (3b3f9eff) Slicer/Slicer#9097

Merged

3 tasks

hjmjohnson marked this pull request as ready for review April 3, 2026 13:41

hjmjohnson force-pushed the fix-non-pod-constexpr-strings branch from 1e01702 to 3e92050 Compare April 3, 2026 13:41

jamesobutler requested a review from lassoan April 3, 2026 16:44

hjmjohnson force-pushed the fix-non-pod-constexpr-strings branch from 3e92050 to d67254c Compare April 13, 2026 19:28

hjmjohnson force-pushed the fix-non-pod-constexpr-strings branch 2 times, most recently from 8aed437 to f9060b7 Compare April 27, 2026 12:19

lassoan mentioned this pull request Jul 18, 2026

STYLE: Replace non-POD string constants with constexpr QLatin1String #1440

Open

lassoan reviewed Jul 18, 2026

View reviewed changes

hjmjohnson closed this Aug 30, 2026

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STYLE: Replace non-POD string constants with constexpr QLatin1String - #1410

STYLE: Replace non-POD string constants with constexpr QLatin1String#1410
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Summary

Problem

Approach

Files Changed

Comparison with PR #1398

Testing

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hjmjohnson commented Apr 3, 2026

CTK Validation Report for PR #1410

Validation Actions Performed

CTK-in-Slicer Build Detail (classified warnings)

Slicer Test Detail (classified failures)

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