cppcheck found some issues:

/data/runtests/work/sources/syncevolution/src/backends/signon/signon-accounts.cpp:130:
cppcheck performance: stlcstrReturn - Returning the result of c_str() in a
function that returns std::string is slow and redundant.
/data/runtests/work/sources/syncevolution/src/backends/signon/signon-accounts.cpp:154:
cppcheck performance: stlcstrReturn - Returning the result of c_str() in a
function that returns std::string is slow and redundant.
Checking
/data/runtests/work/sources/syncevolution/src/backends/signon/signon-accounts.cpp:
USE_SIGNON...
Checking
/data/runtests/work/sources/syncevolution/src/backends/pbap/PbapSyncSource.cpp:
ENABLE_PBAP...
/data/runtests/work/sources/syncevolution/src/backends/signon/signon.cpp:77:
cppcheck performance: stlcstrReturn - Returning the result of c_str() in a
function that returns std::string is slow and redundant.
/data/runtests/work/sources/syncevolution/src/backends/signon/signon.cpp:119:
cppcheck performance: stlcstrReturn - Returning the result of c_str() in a
function that returns std::string is slow and redundant.