Error message written to output file when compiling with clang?

I've got an odd scenario I havent seen before. Periodically when I perform a compile with clang I end up with an incorrectly generated output file.

The output file, for example a .o file, will intermittently have a string like the following example at the start of the file beginning at offset 0.

~/projects/foo$ head someBrokenFile.o

<hostname_of_my_dev_machine>:66850:0x110522e00:1690395486�C�]�f�UH��AWAVAUATSH���L����H��(���L�uH�H�H�E�M��� A�>�A�����H����H��(������Ӆ���E��x �u{A����A��	|wE

The <hostname>:<4-5 digit number>:<some hex offset>:<some 10 digit number> is prepended to the beginning of what is supposed to be a a binary file.

The <hostname> field is always specific to the machine I am running the compile on. The second field looks like it may be the PID of an OS level process. The third I have no idea - an error code? The fourth field I suspect is an OS level timestamp.

I'm new to development using Xcode and I'm wondering if this is some sort of failure mode/output from Xcode tools when 'something bad has happened'.

Does this unexpected and intermittent data being written to my output files from clang look familiar to anyone?

Error message written to output file when compiling with clang?
 
 
Q