AIX: C++ application with shared Qt5Core lib dependency has thread-local-storage runtime issue

Question

I am on IBM AIX-7.2 and have this sample C++ code:

#include <QtCore/QCoreApplication>
#include <QtCore/QDebug>
#include <QtCore/QDateTime>
#include <cstring>
int main(int argc, char *argv[]) {
 QCoreApplication app(argc, argv);
 char const* utf8Str = "Logging output using Qt5Core";
 QString logMe = QString::fromUtf8(utf8Str, std::strlen(utf8Str));
 // Get the current date and time
 QDateTime currentDateTime = QDateTime::currentDateTime();
 // Format the date and time as a string
 QString timeStamp = currentDateTime.toString("yyyy-MM-dd hh:mm:ss.zzz");
 // Output the log message with the time stamp
 qDebug() << "[" << timeStamp << "]" << logMe;
 app.exit();
 return 0;
}

to test with Qt5. However, I always get a run-time error:

 0509-187 The local-exec model was used for thread-local
 storage, but the module is not the main program.
 0509-193 Examine the .loader section header with the
 'dump -Hv' command.

no matter which tls-model option is use for that application. I am using gcc-11 on AIX (unfortunately, I cannot use gnu-ld, but the IBM ld only), and I also tried the different tls-models when compiling QT5 itself from source.

For reference, I checked the manual page of gcc-11, as well as the following hints: about thread local storage IBM guide on tls

I would appreciate any more pointers or hints, as I am out of ideas right now ...

I tried the following (always with -maix64, so 64bit-mode):

1. provide TLS models via -ftls-model= to the compilation of the app
2. same for building Qt5 itself
3. different combinations of -f[no-]pic, -fpie, -fPIC, -f[no-]extern-tls-init
4. -D_THREAD_SAFE yes/no
5. -Wl,-bbigtls or -Wl,-bbigtoc

• Lorinczy Zsigmond: Please quote the messages before these too, where it states the name of the problematic shared object.
• cellist: ./qlogging exec(): 0509-036 Cannot load program ./qlogging because of the following errors: 0509-150 Dependent module libQt5Cored.so could not be loaded. 0509-187 The local-exec model was used for thread-local storage, but the module is not the main program. (FYI: I stripped the path to libQt5Cored.so)
• Lorinczy Zsigmond: Where does this Qt come from? Have you compiled it from source?
• cellist: Yes, I compiled it from source, also trying different thread-local-storage models along the way, and tried with each of these versions, but without any success, unfortunately.
• Lorinczy Zsigmond: When building QT (or any shared object) use compiler options -DPIC -fPIC -pthread.

Answer 1

This problem occurs if you compile shared objects without compiler-flags -fPIC -DPIC. Also -pthread flag should be used at every compilation and linkage step.