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# gas
## Frequently used directives
- `.byte`, `.2byte`, `.4byte`, `.8byte` to define a N byte value
```x86asm
.byte 0xaa
.2byte 0xaabb
.2byte 0xaa, 0xbb
.4byte 0xaabbccdd
.8byte 0xaabbccdd11223344
```
- `.ascii` to define an ascii string
```x86asm
.ascii "foo" ; allocates 3 bytes
```
- `.asciz` to define an ascii string with `'\0'` terminator
```x86asm
.asciz "foo" ; allocates 4 bytes (str + \0)
```
- `.macro` to define assembler macros. Arguments are accessed with the
`\arg` syntax.
```x86asm
.macro defstr name str
\name:
.ascii "\str"
\name\()_len:
.8byte . - \name
.endm
; use as
defstr foo, "foobar"
```
> Use `\()` to concatenate macro argument and literal.
- [GNU Assembler][gas_doc]
- [GNU Assembler Directives][gas_directives]
- [GNU Assembler `x86_64` dependent features][gas_x86_64]
[gas_doc]: https://sourceware.org/binutils/docs/as
[gas_directives]: https://sourceware.org/binutils/docs/as/Pseudo-Ops.html#Pseudo-Ops
[gas_x86_64]: https://sourceware.org/binutils/docs/as/i386_002dDependent.html
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