I am fiddling with Qt and, as always, writing and compiling the code on the phone itself. All was hunky-dory for many edit-and-compile iterations until I suddenly out of the blue started receiving this error:
This is the code that triggered all the fuss:
Removing the blue bit makes it behave again. I even suspected some hidden non-ASCII sneaking into the code somewhere, so I deleted the offending lines completely and wrote them again from scratch. Same results.

Now here comes the interesting part. Various vays of editing the code got rid of the error:

• Add a declaration of something involved at the beginning of the function. It does not need to be used, as long as the con/destructor is being called. An int was not enogh, but e.g. an QStringList did the trick.
• Split the string literal in one of the blue lines to something like QString("k") + "Hz".
• Change switch(index) to switch(index+1), with obvious changes to the case labels.

What did not work:

• Change the string literals.
• Add an another addItem line with a string literal argument.
• Remove one of the blue lines (removing both worked though).

All this points me in the direction of code size. In all cases that fixed the problem, a significant amount of additional code was generated or removed. My theory is that the compiler generates the code in multiples of X bytes and adds padding as necessary, and that the orn r3,r3,#127 instruction is somehow involved in that. Adding or removing enough code changes the padding and avoids using the instruction.

Does anyone have a better explanation or, better still, a solution? I am using gcc 4.6.1 from extras-devel, if that makes any difference, and am using the CFLAGS trick suggested here to build Qt on the phone. Perhaps another flag is required?