Connecting to QProcess::finished¶

Date

2015-05-18

If you are trying to connect a C++11 closure to the finished signal in QProcess, you will most probably run into the standard error message on overloaded Qt signals. Trying to compile:

connect(some_process, &QProcess::finished,
  [](int,QProcess::ExitStatus){ /* […] */ });

will generate the following error:

error: no matching function for call to
‘[…]::connect(QProcess*&, <unresolved overloaded function type>,
              […]::<lambda(int, QProcess::ExitStatus)>)’

with GCC and:

error: no matching member function for call to 'connect'

with clang. The latter is quite concise but the former clearly shows the overloading problem with unresolved overloaded function.

Well, the documentation does not give any hint to an overloaded signal, but a glance at the headers confirms it:

void finished(int exitCode); // ### Qt 6: merge the two signals […]
void finished(int exitCode, QProcess::ExitStatus exitStatus);

It seems we might see the problem solved in Qt 6. For the time being you can solve this problem by making the overloaded member explicit:

connect(some_process,
  static_cast<void(QProcess::*)(int,QProcess::ExitStatus)>(&QProcess::finished),
  [](int,QProcess::ExitStatus){ /* […] */ });

But, yes, it’s a tad verbose.