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Doc: fix null pointer passing to fprintf

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When these docs were written, the context.file and context.function
pointers were never null. But in commit d78fb442d7
(Qt 5.4), we made the logging pass null pointers in release builds. The
C standard does not say that passing null pointers is permitted. In
fact, it says "If no l length modifier is present, the argument shall be
a pointer to the initial element of an array of character type." and
that's pretty explicit that it needs to point to the initial element of
a string.

Fixes: QTBUG-72478
Change-Id: I4ac1156702324f0fb814fffd156f624ffefa1445
Reviewed-by: Topi Reiniö <topi.reinio@qt.io>
This commit is contained in:
Thiago Macieira 2018-12-11 12:48:12 -08:00
parent 3c3a2eb3ce
commit 3e4f8aa8f4
1 changed files with 7 additions and 5 deletions
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12
src/corelib/doc/snippets/code/src_corelib_global_qglobal.cpp
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@ -279,21 +279,23 @@ const TInputType &myMin(const TInputType &value1, const TInputType &value2)
void myMessageOutput(QtMsgType type, const QMessageLogContext &context, const QString &msg)
{
QByteArray localMsg = msg.toLocal8Bit();
const char *file = context.file ? context.file : "";
const char *function = context.function ? context.function : "";
switch (type) {
case QtDebugMsg:
fprintf(stderr, "Debug: %s (%s:%u, %s)\n", localMsg.constData(), context.file, context.line, context.function);
fprintf(stderr, "Debug: %s (%s:%u, %s)\n", localMsg.constData(), file, context.line, function);
break;
case QtInfoMsg:
fprintf(stderr, "Info: %s (%s:%u, %s)\n", localMsg.constData(), context.file, context.line, context.function);
fprintf(stderr, "Info: %s (%s:%u, %s)\n", localMsg.constData(), file, context.line, function);
break;
case QtWarningMsg:
fprintf(stderr, "Warning: %s (%s:%u, %s)\n", localMsg.constData(), context.file, context.line, context.function);
fprintf(stderr, "Warning: %s (%s:%u, %s)\n", localMsg.constData(), file, context.line, function);
break;
case QtCriticalMsg:
fprintf(stderr, "Critical: %s (%s:%u, %s)\n", localMsg.constData(), context.file, context.line, context.function);
fprintf(stderr, "Critical: %s (%s:%u, %s)\n", localMsg.constData(), file, context.line, function);
break;
case QtFatalMsg:
fprintf(stderr, "Fatal: %s (%s:%u, %s)\n", localMsg.constData(), context.file, context.line, context.function);
fprintf(stderr, "Fatal: %s (%s:%u, %s)\n", localMsg.constData(), file, context.line, function);
break;
}
}