Invalid image produced by ilasm in .NET 9.0

[jkotas]

Repro

1. Create a new C# console project
   mkdir C:\work\ilx64
   cd C:\work\ilx64
   dotnet new console

2. Build and run the created project
   dotnet run

3. Move to the output folder
   cd .\bin\Debug\net9.0\

4. Verify that ilx64.dll exists
   dir ilx64.dll

5. Decompile with ildasm
   C:\Users<username>.nuget\packages\runtime.win-x64.microsoft.netcore.ildasm\8.0.0\runtimes\win-x64\native\ildasm.exe /out:ilx64.il .\ilx64.dll

6. Run /pe64 with ilasm version 8.0.0 Compile with /x64
   C:\Users<username>.nuget\packages\runtime.win-x64.microsoft.netcore.ilasm\8.0.0\runtimes\win-x64\native\ilasm.exe /pe64 /x64 /out:ilx64.dll ilx64.il

7. Check operation ※Operates normally
   dotnet .\ilx64.dll

8. Compile with /pe64 /x64 in version 9.0.0 of ilasm
   C:\Users<username>.nuget\packages\runtime.win-x64.microsoft.netcore.ilasm\9.0.0\runtimes\win-x64\native\ilasm.exe /pe64 /x64 /out:ilx64.dll ilx64.il

9. Check operation ※BadImageFormatException occurs
   dotnet .\ilx64.dll

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[jkotas]

More information

I guess this may be due to the removal of elements srRelocIA64Imm64 from CeeSectionRelocType enum without adjusting subsequent values.
https://github.com/dotnet/runtime/pull/90752/files#diff-301d890a871c8cbb7bf5b9a5002920a00ab13c2a92cb61bff61cdce22be0be82

typedef enum {
    // generate only a section-relative reloc, nothing into .reloc section
    srRelocAbsolute,

    // generate a .reloc for a pointer sized location,
    // This is transformed into BASED_HIGHLOW or BASED_DIR64 based on the platform
    srRelocHighLow = 3,

    // generate a .reloc for the top 16-bits of a 32 bit number, where the
    // bottom 16 bits are included in the next word in the .reloc table
    srRelocHighAdj,     // Never Used

    // generate a token map relocation, nothing into .reloc section
    srRelocMapToken,

    // relative address fixup
    srRelocRelative,

    // Generate only a section-relative reloc, nothing into .reloc
    // section.  This reloc is relative to the file position of the
    // section, not the section's virtual address.
    srRelocFilePos,

    // code relative address fixup
    srRelocCodeRelative,

    // generate a .reloc for a 64 bit address in an ia64 movl instruction
    srRelocIA64Imm64,

    // generate a .reloc for a 64 bit address
    srRelocDir64,

    // generate a .reloc for a 25-bit PC relative address in an ia64 br.call instruction
    srRelocIA64PcRel25,

    // generate a .reloc for a 64-bit PC relative address in an ia64 brl.call instruction
    srRelocIA64PcRel64,

    // generate a 30-bit section-relative reloc, used for tagged pointer values
    srRelocAbsoluteTagged,

    // A sentinel value to help ensure any additions to this enum are reflected
    // in PEWriter.cpp's RelocName array.
    srRelocSentinel,

    // Flags that can be used with the above reloc types

    // do not emit base reloc
    srNoBaseReloc = 0x4000,

    // pre-fixup contents of memory are ptr rather than a section offset
    srRelocPtr = 0x8000,

    // legal enums which include the Ptr flag
    srRelocAbsolutePtr = srRelocPtr + srRelocAbsolute,
    srRelocHighLowPtr = srRelocPtr + srRelocHighLow,
    srRelocRelativePtr = srRelocPtr + srRelocRelative,
    srRelocIA64Imm64Ptr = srRelocPtr + srRelocIA64Imm64,
    srRelocDir64Ptr = srRelocPtr + srRelocDir64,

} CeeSectionRelocType;