AOT compiler generates invalid assembler code for Mac Catalyst in .NET 9

[rolfbjarne]

Description

AOT compiler generates invalid assembler code for Mac Catalyst in .NET 9

Reproduction Steps

Test case: aot-compiler-test-case-fa0f17e.zip

Unzip and run test.sh. The script will download the AOT compiler for 9.0.0-alpha.1.24066.33 and AOT compile the file linked/Microsoft.Maui.Controls.dll + (try to) compile the resulting assembler code.

Expected behavior

Valid assembler code.

Actual behavior

Microsoft.Maui.Controls.dll.s:91707:10: error: unexpected token in '.loc' directive
.loc 107 -8 0
         ^
Microsoft.Maui.Controls.dll.s:224390:10: error: unexpected token in '.loc' directive
.loc 249 -11 0
         ^
Microsoft.Maui.Controls.dll.s:445252:10: error: unexpected token in '.loc' directive
.loc 431 -3 0
         ^
Microsoft.Maui.Controls.dll.s:452970:10: error: unexpected token in '.loc' directive
.loc 445 -44 0 prologue_end
         ^

Resulting .s file:
Microsoft.Maui.Controls.dll.s.zip

Regression?

Yes, this works in .NET 8.

Known Workarounds

None

Configuration

9.0.0-alpha.1.24066.33

Other information

This is blocking MAUI from building packages for .NET 9.

[rolfbjarne]

CC @vargaz

[rolfbjarne]

Looks like loc->row overflows here?

runtime/src/mono/mono/mini/aot-compiler.c

Line 6797 in 971ebdb

fprintf (acfg->fp, ".loc %d %d 0%s\n", findex, loc->row, options);

It's defined as a uint32_t:

runtime/src/native/public/mono/metadata/details/mono-debug-types.h

Line 106 in 971ebdb

uint32_t row, column;

[steveisok]

@vargaz can you please look into this?

[vargaz]

This appears to be a problem with either the debug info in the pdb file, or its decoding. Need more time to investigate, added a workaround in a PR.

[vargaz]

I think this is caused by:
#96497

The additional iloffset < offset check causes us to skip a mono_metadata_decode_value () call, messing up the decoding of later entries.

[vargaz]

The problematic PR was reverted on master/9.0.