File - Using as
Description: Using as

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### 7.53 `.file`

There are two different versions of the `.file` directive. Targets that support DWARF2 line number information use the DWARF2 version of `.file`. Other targets use the default version.

#### Default Version

This version of the `.file` directive tells `as` that we are about to start a new logical file. The syntax is:

         .file string

string is the new file name. In general, the filename is recognized whether or not it is surrounded by quotes ‘`"`’; but if you wish to specify an empty file name, you must give the quotes–`""`. This statement may go away in future: it is only recognized to be compatible with old `as` programs.

#### DWARF2 Version

When emitting DWARF2 line number information, `.file` assigns filenames to the `.debug_line` file name table. The syntax is:

         .file fileno filename

The fileno operand should be a unique positive integer to use as the index of the entry in the table. The filename operand is a C string literal.

The detail of filename indices is exposed to the user because the filename table is shared with the `.debug_info` section of the DWARF2 debugging information, and thus the user must know the exact indices that table entries will have.