Raspberry Pi 3 bare metal: unexpected behaviour from arrays and switch statements

I currently have a simple program that sets up a framebuffer that can be written to.

I am encountering behaviour where values stored i arrays, once retrieved, come back as seemingly random values, with no relation to the originals. I have also noticed some similarly strange and.unexpected behaviour from switch statements - I suspect this has something to do with how both arrays and switch statements are statically allocated in memory.

As an example, here I have some code that should draw a hardcoded number, followed by 7 other hardcoded numbers that have been stored in an array:

unsigned int cols[7] = { 0xFFFF0000, 0xFFFF7F00, 0xFFFFFF00, 0xFF00FF00, 0xFF0000FF, 0xFF4B0082, 0xFF9400D3 };
drawNum(&display, 0x1234ABCD);
for (int i=0; i<7; i++)
  drawNum(&display, cols[i]);

The first drawNum() call with the hardcoded value works fine, but all of the calls with array accesses give seemingly random results.

Assigning the array values at runtime doesn't have this problem, like so:

unsigned int cols[7];
cols[0] = 0xFFFF0000;
cols[1] = 0xFFFF7F00;
cols[2] = 0xFFFFFF00;
cols[3] = 0xFF00FF00;
cols[4] = 0xFF0000FF;
cols[5] = 0xFF4B0082;
cols[6] = 0xFF9400D3;
drawNum(&display, 0x1234ABCD);
drawNum(&display, (int)cols);
for (int i=0; i<7; i++)
  drawNum(&display, cols[i]);

I've also experienced similarly unpredictable behaviour when returning values from switch statements.

I cannot say for sure, but this leads me to believe that this is a problem with the compiler or linker being used - I am using arm-none-eabi.

Just a shot in the dark, but you may want to try a different value in your array where the highest bit is 0 instead of 1 like in your hardcoded example.

unsigned int cols[7] = { 0x7FFF0000, 0x7FFF7F00, 0x7FFFFF00, 0x7F00FF00, 0x7F0000FF, 0x7F4B0082, 0x7F9400D3 };

This is assuming that drawNum takes an int instead of an unsigned int. You might just have a conversion problem. Without seeing what drawNum does it's hard to say.