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Diffstat (limited to 'docs/checks/README-qstring-arg.md')
| -rw-r--r-- | docs/checks/README-qstring-arg.md | 39 |
1 files changed, 39 insertions, 0 deletions
diff --git a/docs/checks/README-qstring-arg.md b/docs/checks/README-qstring-arg.md new file mode 100644 index 00000000..819a97cf --- /dev/null +++ b/docs/checks/README-qstring-arg.md @@ -0,0 +1,39 @@ +# qstring-arg + +Implements two warnings: + +1. Detects when you're using chained `QString::arg()` calls and should instead use the multi-arg overload to save memory allocations + + QString("%1 %2").arg(a).arg(b); + QString("%1 %2").arg(a, b); // one less temporary heap allocation + +2. Detects when you're using misleading `QString::arg()` overloads + + QString arg(qlonglong a, int fieldwidth = 0, int base = 10, QChar fillChar = QLatin1Char(' ')) const + QString arg(qulonglong a, int fieldwidth = 0, int base = 10, QChar fillChar = QLatin1Char(' ')) const + QString arg(long a, int fieldwidth = 0, int base=10, QChar fillChar = QLatin1Char(' ')) const + QString arg(ulong a, int fieldwidth = 0, int base=10, QChar fillChar = QLatin1Char(' ')) const + QString arg(int a, int fieldWidth = 0, int base = 10, QChar fillChar = QLatin1Char(' ')) const + QString arg(uint a, int fieldWidth = 0, int base = 10, QChar fillChar = QLatin1Char(' ')) const + QString arg(short a, int fieldWidth = 0, int base = 10, QChar fillChar = QLatin1Char(' ')) const + QString arg(ushort a, int fieldWidth = 0, int base = 10, QChar fillChar = QLatin1Char(' ')) const + QString arg(double a, int fieldWidth = 0, char fmt = 'g', int prec = -1, QChar fillChar = QLatin1Char(' ')) const + QString arg(char a, int fieldWidth = 0, QChar fillChar = QLatin1Char(' ')) const + QString arg(QChar a, int fieldWidth = 0, QChar fillChar = QLatin1Char(' ')) const + QString arg(const QString &a, int fieldWidth = 0, QChar fillChar = QLatin1Char(' ')) const + +because they are commonly misused, for example: + + int hours = ...; + int minutes = ...; + // This won't do what you think it would at first glance. + QString s("The time is %1:%2").arg(hours, minutes); + +To reduce false positives, some cases won't be warned about: + + str.arg(hours, 2); // User explicitly used a integer literal, it's probably fine + str.arg(foo); // We're only after cases where the second argument (or further) is specified, so this is safe + str.arg(foo, width); // Second argument is named width, or contains the name "width", it's safe. Same for third argument and "base". + +Using these misleading overloads is perfectly valid, so only warning (1) is enabled by default. +To enable warning (2), `export CLAZY_EXTRA_OPTIONS="qstring-arg-fillChar-overloads"` |