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•Created by Marvee Amasi on 8/15/2024 in #firmware-and-baremetal

Segmentation Fault in C Function Printing Double from Assembly Code

@Marvee Amasi It sounds like you’re dealing with an alignment issue or possibly an issue with how the double is being accessed in memory. When you cast a long to a double, there’s a chance that the address isn’t properly aligned for accessing double-precision floating point numbers, especially on a 64-bit system. A quick test would be to ensure that val is aligned correctly before casting it to a double. You can add an assertion to check the alignment

case 6:
  assert(val % sizeof(double) == 0);  // Ensure alignment
  c = *(double*) val;
  printf("%f\n", c); /* seg fault */
  break;

case 6:
  assert(val % sizeof(double) == 0);  // Ensure alignment
  c = *(double*) val;
  printf("%f\n", c); /* seg fault */
  break;

If the assertion fails, then the address val isn’t properly aligned for a double, which would cause the segmentation fault. Also, consider checking how the value of val is being passed from the assembly code. If there's any chance that it’s being misaligned before it’s passed to the C function.

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