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Diffstat (limited to 'src/checks/level2/README-qstring-allocations.md')
| -rw-r--r-- | src/checks/level2/README-qstring-allocations.md | 49 |
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diff --git a/src/checks/level2/README-qstring-allocations.md b/src/checks/level2/README-qstring-allocations.md deleted file mode 100644 index fda4278e..00000000 --- a/src/checks/level2/README-qstring-allocations.md +++ /dev/null @@ -1,49 +0,0 @@ -# qstring-unneeded-heap-allocations - -Finds places with unneeded memory allocations due to temporary `QString`s. - -Here's a summary of usages that allocate: - -1. `QString s = "foo"; // Allocates, use QStringLiteral("foo") instead` - -2. `QString s = QLatin1String("foo"); // Allocates, use QStringLiteral("foo") instead` - - 2.1 `QString s = QLatin1String(""); // No allocation. QString is optimized for this case, so it's safe for empty literals` - -3. `QString s = QStringLiteral("foo"); // No allocation` - -4. `QString s = QString::fromLatin1("foo"); // Allocates, use QStringLiteral` - -5. `QString s = QString::fromUtf8("foo"); // Allocates, use QStringLiteral` - -6. `s == "foo" // Allocates, use QLatin1String` - -7. `s == QLatin1String("foo) // No allocation` - -8. `s == QStringLiteral("foo") // No allocation` - -9. `QString {"append", "compare", "endsWith", "startsWith", "indexOf", "insert",` - ` "lastIndexOf", "prepend", "replace", "contains" } // They all have QLatin1String overloads, so passing a QLatin1String is ok.` - -10. `QString::fromLatin1("foo %1").arg(bar) // Allocates twice, replacing with QStringLiteral makes it allocate only once.` - - -#### Fixits - - fix-qlatin1string-allocations // To replace QLatin1String with QStringLiteral only where it was allocating before - fix-fromLatin1_fromUtf8-allocations // To replace fromLatin1() and fromUtf8() so it doesn't allocate - fix-fromCharPtrAllocations // To replace raw string literals so it doesn't allocate - - Example: - export CLAZY_FIXIT="fix-fromCharPtrAllocations" - -#### Pitfalls - -- `QStringLiteral` might make your app crash at exit if plugins are involved. -See: -<https://blogs.kde.org/2015/11/05/qregexp-qstringliteral-crash-exit> and -<http://lists.qt-project.org/pipermail/development/2015-November/023681.html> - -- Also note that MSVC crashes when `QStringLiteral` is used inside initializer lists. For that reason no warning or fixit is emitted for this case unless you set an env variable: - - export CLAZY_EXTRA_OPTIONS="qstring-allocations-no-msvc-compat" |