mono/mono · critical

AOT of image %s failed.

Error message

AOT of image %s failed.

What it means

In AOT mode, mono_compile_assembly returned non-zero for a specific assembly argument, meaning Ahead-Of-Time compilation of that image failed. The driver prints the offending path and exits(1). The root cause is inside the AOT compiler (LLVM/Mono backend, codegen, or signature/resolution errors) and is usually detailed by earlier stderr output.

Source

Thrown at mono/mini/driver.c:1447

				} else {
					fprintf (stderr, "Can not open image %s\n", main_args->argv [i]);
					exit (1);
				}
			}
			/* Check that the assembly loaded matches the filename */
			{
				MonoImageOpenStatus status;
				MonoImage *img;

				img = mono_image_open (main_args->argv [i], &status);
				if (img && strcmp (img->name, assembly->image->name)) {
					fprintf (stderr, "Error: Loaded assembly '%s' doesn't match original file name '%s'. Set MONO_PATH to the assembly's location.\n", assembly->image->name, img->name);
					exit (1);
				}
			}
			res = mono_compile_assembly (assembly, main_args->opts, main_args->aot_options, &aot_state);
			if (res != 0) {
				fprintf (stderr, "AOT of image %s failed.\n", main_args->argv [i]);
				exit (1);
			}
		}
		if (aot_state) {
			res = mono_compile_deferred_assemblies (main_args->opts, main_args->aot_options, &aot_state);
			if (res != 0) {
				fprintf (stderr, "AOT of mode-specific deferred assemblies failed.\n");
				exit (1);
			}
		}
	} else {
		assembly = mono_domain_assembly_open_internal (main_args->domain, mono_domain_default_alc (main_args->domain), main_args->file);
		if (!assembly){
			fprintf (stderr, "Can not open image %s\n", main_args->file);
			exit (1);
		}

		/* 

View on GitHub (pinned to 0f53e9e151)

Solutions

1. Read the full stderr above this line: the AOT compiler prints the specific method/reason that failed.
2. For cross-compilation, install the correct target cross-toolchain and pass --llvm or the right mtriple (--aot=mtriple=...).
3. Exclude the failing assembly from the AOT batch, or AOT it separately with conservative flags (--aot=llvm-level=0, no-llvm).
4. Update Mono/framework assemblies to matching versions and retry.

Example fix

# before
mono --aot MyApp.dll   // mono_compile_assembly != 0
# after: read the error above, then disable LLVM for that image
mono --aot=llvm=false MyApp.dll

# Smoke-AOT a single image to surface the precise failure first
monodis --assembly "$IMG" >/dev/null 2>&1 || { echo "bad image: $IMG"; exit 1; }

When it happens

Trigger: AOT-compiling an assembly that references types/members unavailable at AOT time, uses unsupported constructs for the target arch, fails LLVM lowering, or has a method the AOT compiler cannot process. mono_compile_assembly returns the failure code.

Common situations: Cross-AOT targeting a different arch without the right cross toolchain; AOT-ing an assembly that depends on P/Invoke or dynamic code; LLVM disabled/missing where the method requires it; version skew between framework assemblies and the one being compiled.

Related errors

• AOT of mode-specific deferred assemblies failed.
• Can not open image %s
• Error: Loaded assembly '%s' doesn't match original file name
• max-heap-size must be at least %dMb.
• max-heap-size must be an integer.

AI-assisted analysis of mono/mono@0f53e9e151 (2026-08-13). Data as JSON: /api/errors/36e6cc346cdc283d. Report an issue: GitHub.