What causes "exiting, no ASCII hex found\n" in NationalSecurityAgency/ghidra?

Ensure the stdin input supplies both an address line and a bytes line before EOF.

exiting, no ASCII hex found\n

Error message

exiting, no ASCII hex found\n

What it means

gdis stdin-mode end-of-input message. In stdin_mode the program reads an address line then a bytes/options line via fgets; when the second fgets returns NULL (EOF / empty input) it prints 'exiting, no ASCII hex found' and returns 0 to finish the loop. This is a normal termination path, not a crash, though the wording reads like an error.

Source

Thrown at GPL/GnuDisassembler/src/gdis/c/disasm_1.c:360

					strncpy(byteStringBuffer,bytesAndOptionsBuffer,(int) (p - bytesAndOptionsBuffer));
					strncpy(disassemblerOptions,p+1,sizeof(disassemblerOptions));
					p = strchr(disassemblerOptions,'\n');
					if (p){
						*p = '\0';
					}
				}
				else {
					//no "*" in the string, so no disassembly options
					//replace newline with null terminator
					strncpy(byteStringBuffer, bytesAndOptionsBuffer, sizeof(byteStringBuffer));
					p = strchr(byteStringBuffer,'\n');
					if (p){
						*p = '\0';
					}
				}
			}
			else {
				fprintf(stderr, "exiting, no ASCII hex found\n");
				return 0; // finished! #TODO
			}
		}
		else {
			if(strlen(byteString) > BYTE_BUFFER_SIZE*2) {
				fprintf(stderr, "Max ascii string size is %d you provided: %lu chars. Exiting.\n", BYTE_BUFFER_SIZE*2,
						strlen(byteString));
				exit(-1);
			}
			strncpy(byteStringBuffer, byteString, BYTE_BUFFER_SIZE*2);
			stdin_mode = 0; // break out of the while loop
		}

		int size = strlen(byteStringBuffer);
		if((size % 2) != 0){
			fprintf(stderr, "need even-number of ascii chars for byte-stream: (offset: %08lx, %s, %ld)\n", offset, byteStringBuffer, strlen(byteStringBuffer));
			exit(-1);
		}

View on GitHub (pinned to d5f144c24d)

Solutions

Ensure the stdin input supplies both an address line and a bytes line before EOF.
If interactive, type or paste the hex byte string instead of closing the stream.
Fix the upstream producer so it always emits the bytes line.
Use argument mode (argc >= 8) instead of stdin mode for deterministic input.

Example fix

# before (stdin truncated)
$ printf '400000\n' | gdis ...   # only address line -> no ASCII hex found

# after (address + bytes)
$ printf '400000\n90909090\n' | gdis ...

Defensive patterns

Strategy: validation

Validate before calling

// ensure stdin input has both lines before processing
if (!fgets(addr, sizeof addr, stdin) || !fgets(bytes, sizeof bytes, stdin)) {
  return 0; // treat as clean EOF
}

Prevention

Producers must always emit address + bytes lines.
Prefer argument mode for deterministic inputs.
Detect EOF cleanly rather than treating it as an error.

When it happens

Trigger: Running gdis in interactive/stdin mode and closing the input stream (Ctrl-D) after the address line but before supplying a byte string; piping an input file whose second line is missing or empty.

Common situations: Interactive disassembly session ended by the user; a piped input file truncated to only the address line; a producer process closing its stdout early.

Related errors

AI-assisted analysis of NationalSecurityAgency/ghidra@d5f144c24d (2026-08-14). Data as JSON: /api/errors/44969be81e14bf56. Report an issue: GitHub.