This is a community service post.  When I come across a problem and I can’t find a solution to it on the Internet, I try to put a solution into the public record.  This one is obscure.

When running ilasm I got an exit code of -1073741819 (the fairly generic C0000005 code).  The problem turned out to be due to an incompatible PDB file in the same directory as the input files.  I experienced this running ilasm for .NET 1.1 with a pre-existing .NET 2.0 PDB file from a previous step in our build process.

To be clear: the PDB file that caused the problem had the same base name as the IL being read and assembly being generated.  It appears that ilasm reads the PDB if it already exists, but since the file is incompatible it returns an error.

The solution here was easy: just delete or move the offending PDB.

Note that if you are running ilasm indirectly through the PreEmptive Dotfuscator product, you will see an error like this:

ilasm returned -1073741819

The FAQ at PreEmptive says that this is due to a problem of path depth (i.e., running ilasm too deeply nested in folders).  That may sometimes be the case too.  I don’t know.