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[lucromain]

This issue seems to have been reported by https://www.ccsinfo.com/forum/viewtopic.php?t=58059 several years ago, but I am getting the same error with newer versions of MPLAB X and CCS.

I'm running MPLAB X version 6.15 on Ubuntu Linux 25.10.
Running CCS v5.123

When pressing the "Debug" icon, it usually works the first time after starting mplab x. However, if I stop the simulator, recompile and then try to restart the debugger, compilation always succeeds, but then I get this error:

[Ttelmah]

it sounds to me like a permission issue.
I suggest you ask CCS themselves. Very few Unix/Linus users, and
your particular configuration will probably be unique.
Suggest though you just try changing the permissions on the working
directory so that everybody has read and write permissions here, and
see if that helps.

[lucromain]

I root cause the problem and now able to run debug successfully, including breakpoints and watches. I'm using MPLAB X v6.15.

In MPLAB X version v6.30, there are issues with breakpoints. The debugger does not stop on breakpoints. Therefore version v6.15 is what I'll keep using going forward.

I used ChatGPT to analyze the .cof file. Here are the results:

Findings

I inspected the generated .cof file and found that the symbol table is structurally present and contains expected symbols, but enum constants appear to be emitted with suspicious COFF metadata.

Problematic source:

enum state_enum {
idle,
tone_start,
tone_on,
tone_tail,
};

In the COFF symbol table, these enum members appear as consecutive symbol entries with:

storage class = 0x10
aux count (n_numaux) = 0xB8 (184)

Example decoded entries:

idle class=0x10 numaux=184
tone_start class=0x10 numaux=184
tone_on class=0x10 numaux=184
tone_tail class=0x10 numaux=184

This aux count appears invalid or nonstandard.

MPLAB X seems to interpret these as standard COFF symbol entries and attempts to read 184 auxiliary records, which likely causes the parser to walk past the symbol table bounds and crash.

Reproduction
Define a global enum like:
enum state_enum {
idle,
tone_start,
tone_on,
tone_tail,
};
Build with debug output enabled (.cof).
Open in MPLAB X debugger/simulator.
Watch window fails to populate or disappears; MPLAB may throw a CoffReaderC18.BuildSymbolTable exception.

Workaround

Replacing the enum with preprocessor constants avoids the issue:

#define STATE_IDLE 0
#define STATE_TONE_START 1
#define STATE_TONE_ON 2
#define STATE_TONE_TAIL 3

int8 state;

With this change, debugger watch symbols behave normally.