byexample

Write snippets of code in your documentation and execute them as regression tests.

View project on GitHub

iasm: the interactive assembler

Run the iasm examples calling byexample as:

$ byexample -l iasm your-file-here                # byexample: +skip

You will have to install iasm first:

$ pip install iasm      # byexample: +skip

Or you can download the code from here

Stability: experimental - non backward compatibility changes are possible or even removal between versions (even patch versions).

New in byexample 10.1.0.

Versions tested

We tested byexample with the following versions of the language and the underlying runner or interpreter:

Language Runner/Interpreter
latest 0.1.3

Set architecture and operation mode

iasm is capable to emulate different architectures.

The settings can be passed to iasm from the command line of byexample. Once set they cannot be changed at runtime.

$ byexample -l iasm -o '+iasm-arch=x86 +iasm-mode=64 +iasm-code-size=102400 +iasm-pc=0' test/ds/iasm.md  # byexample: +timeout=8
<...>
[PASS] Pass: 1 Fail: 0 Skip: 0

See the iasm documentation for more information about those.

Find interactive examples

For iasm, byexample uses the :> string as the primary prompt and -> as the secondary prompt.

In iasm the example is compiled and executed as the architecture configured on start up, ARM by default:

:> mov r0, #4
:> mov r1, #8

Examples that begin with ;! are executed as Python statement that can operate with the registers and with the memory M:

:> ;! print(r0 + r1)
12

Showing the registers

iasm allows you to show the values of the registers by name or pattern.

:> ;! show('r[0-9]', 'r1[0-9]')
------  -  ------  -  ------  -  ------  -----
    r0  4  r1      8  r2      0  r3      0
    r4  0  r5      0  r6      0  r7      0
    r8  0  r9/sb   0  r10     0  r11/fp  0
r12/ip  0  r13/sp  0  r14/lr  0  r15/pc  100:4
------  -  ------  -  ------  -  ------  -----

Add stick=True to display those registers every time.

:> ;! show('r[0-3]', stick=True)
--  -  --  -  --  -  --  -
r0  4  r1  8  r2  0  r3  0
--  -  --  -  --  -  --  -

:> mov r2, r1
--  -  --  -  --  -  --  -
r0  4  r1  8  r2  8  r3  0
--  -  --  -  --  -  --  -

Call show(stick=True) to restore the defaults:

:> ;! show(stick=True)

byexample options

The byexample options can be set in the assembly comments (;) and in the Python comments (#):

:> r1024-nonexist    ; byexample: +skip
:> ;! r1024-nonexist  # byexample: +skip

Known limitations

Type text

The type feature (+type) is not supported.

Terminal support

To work with iasm, the ANSI terminal emulator is enabled by default (+term=ansi) and cannot be disabled.

Also, the terminal geometry cannot by changed after launching the interpreter so the option +geometry cannot be used in an example (but it can be used from the command line)

The amount of rows of the terminal has a minimum value of 128 and this limit is really important: if your outputs have more than 128 lines you will need to increase the geometry or the results may be undefined.

The same for the width of the terminal: minimum of 128 columns.

iasm specific options

$ byexample -l iasm --show-options       # byexample: +norm-ws
<...>
iasm's specific options
-----------------------
<...>:
  +iasm-arch <arch>     architecture name (arm, x86, sparc, ...); see iasm
                        documentation.
  +iasm-mode <mode>     mode (arm, 32, 64, ...); see iasm documentation.
  +iasm-code-size <sz>  size of the code segment; see iasm documentation.
  +iasm-pc <addr>       starting address, value of the program counter; see
                        iasm documentation.
<...>