<s>
Bootstrapable	B-Application
builds	I-Application
,	O
a	O
process	O
of	O
compiling	B-Language
software	O
that	O
does	O
n't	O
depend	O
on	O
(	O
compiler	B-Language
)	O
binaries	O
that	O
are	O
n't	O
build	O
from	O
source	O
by	O
this	O
process	O
.	O
</s>
<s>
This	O
process	O
can	O
protect	O
against	O
compiler	B-Language
backdoors	O
:	O
if	O
the	O
build	O
process	O
does	O
n't	O
depend	O
on	O
binary	O
code	O
that	O
is	O
difficult	O
to	O
audit	O
,	O
then	O
a	O
compiler	B-Language
backdoor	O
cannot	O
be	O
hidden	O
in	O
compiler	B-Language
binaries	O
anymore	O
.	O
</s>
<s>
A	O
way	O
to	O
tackle	O
the	O
issue	O
for	O
a	O
Software	B-Application
distributions	I-Application
is	O
to	O
reduce	O
the	O
size	O
of	O
the	O
binaries	O
used	O
to	O
bootstrap	O
the	O
distribution	O
until	O
there	O
are	O
not	O
needed	O
anymore	O
or	O
that	O
the	O
size	O
is	O
small	O
enough	O
to	O
be	O
easily	O
reviewed	O
by	O
humans	O
.	O
</s>
<s>
Many	O
compilers	B-Language
for	O
various	O
programming	O
languages	O
are	O
written	O
in	O
the	O
language	O
they	O
target	O
.	O
</s>
<s>
For	O
instance	O
the	O
official	O
Go	B-Application
compiler(gc )	O
is	O
written	O
in	O
Go	B-Application
.	O
</s>
<s>
So	O
without	O
alternatives	O
compilers	B-Language
compiler	B-Language
like	O
GCC	B-Application
that	O
are	O
written	O
in	O
another	O
programming	O
language	O
(	O
here	O
in	O
C	O
and	O
C++	O
)	O
the	O
go	B-Application
compiler	B-Language
would	O
require	O
a	O
binary	O
of	O
a	O
previous	O
version	O
of	O
the	O
go	B-Application
compiler	B-Language
binary	O
to	O
be	O
built	O
.	O
</s>
<s>
To	O
have	O
bootstrapable	B-Application
builds	I-Application
,	O
it	O
is	O
often	O
possible	O
to	O
find	O
an	O
older	O
versions	O
of	O
the	O
compiler	B-Language
that	O
could	O
be	O
built	O
from	O
sources	O
,	O
and	O
from	O
that	O
,	O
write	O
code	O
to	O
automatically	O
build	O
the	O
next	O
version	O
of	O
the	O
compilers	B-Language
until	O
having	O
a	O
recent	O
version	O
.	O
</s>
<s>
Identifying	O
which	O
version	O
can	O
build	O
which	O
versions	O
is	O
often	O
not	O
trivial	O
and	O
that	O
often	O
result	O
in	O
very	O
long	O
compilation	B-Language
times	O
for	O
the	O
bootstrap	O
procedure	O
.	O
</s>
<s>
Sometimes	O
this	O
also	O
require	O
to	O
maintain	O
older	O
compiler	B-Language
versions	O
and	O
to	O
backport	O
support	O
for	O
newer	O
CPU	O
architectures	O
on	O
older	O
compilers	B-Language
versions	O
to	O
be	O
able	O
to	O
bootstrap	O
these	O
architectures	O
.	O
</s>
<s>
This	O
process	O
can	O
also	O
be	O
replaced	O
or	O
combined	O
with	O
other	O
ways	O
to	O
bootstrap	O
compilers	B-Language
.	O
</s>
<s>
For	O
instance	O
it	O
is	O
also	O
possible	O
to	O
write	O
a	O
new	O
compiler	B-Language
for	O
a	O
language	O
,	O
that	O
is	O
written	O
in	O
another	O
language	O
.	O
</s>
<s>
As	O
for	O
building	O
the	O
first	O
compiler	B-Language
that	O
can	O
build	O
the	O
subsequent	O
compilers	B-Language
,	O
it	O
is	O
possible	O
to	O
reduce	O
the	O
size	O
to	O
a	O
single	O
binary	O
that	O
is	O
less	O
than	O
1	O
Kilobyte	O
and	O
from	O
that	O
use	O
multiple	O
stages	O
in	O
the	O
bootstrapping	O
procedure	O
to	O
be	O
able	O
to	O
build	O
a	O
C	O
compiler	B-Language
,	O
and	O
from	O
that	O
build	O
the	O
other	O
compilers	B-Language
or	O
software	O
.	O
</s>
<s>
The	O
Bootstrapable	B-Application
builds	I-Application
was	O
started	O
in	O
2016	O
as	O
a	O
spin-off	O
of	O
the	O
reproducible	B-Application
builds	I-Application
project	O
.	O
</s>
