I have a "generic" (in terms of queries it accepts) function that does something like

// std::string query = "UPDATE ... (without returning anything)" in this particular case
soci::row row;
soci::statement st = (sql.prepare << query, soci::into(row));
st.execute(false);
while (st.fetch()) {
    // do something with the row - the code is "generic" and should work with queries that return data too
}

in this case, I get a lot of iterations in the while loop which I think are due to multiple variables in the PSQL statement backend being in an undefined state. I stepped through the execution in a debugger and found that:

• during st.execute(false), process_result is false here:
  

  soci/src/backends/postgresql/statement.cpp

  Lines 521 to 526 in b2e4cf3

  	if (process_result)
  	{
  	currentRow_ = 0;
  	rowsToConsume_ = 0;
  	numberOfRows_ = PQntuples(result_);

  
  which causes it to immediately jump to
  

  soci/src/backends/postgresql/statement.cpp

  Lines 545 to 548 in b2e4cf3

  	else
  	{
  	return ef_no_data;
  	}

  
  - which makes sense since no data is indeed produced by an update query. It is, however, skipping the initialization of currentRow_, rowsToConsume_ and numberOfRows_
• then, backend calls from st.fetch() go into
  

  soci/src/backends/postgresql/statement.cpp

  Line 552 in b2e4cf3

  postgresql_statement_backend::fetch(int number)

  
  which uses these uninitialized members in its body, e.g.
  

  soci/src/backends/postgresql/statement.cpp

  Lines 568 to 570 in b2e4cf3

  	currentRow_ += rowsToConsume_;
  	if (currentRow_ >= numberOfRows_)

Documentation does not suggest the return value of execute() to be checked before following it up with fetch(), so I suppose it's not intended behavior and fetch() in my case should've returned false immediately?