...
Many
...
functions
...
require
...
the
...
allocation
...
of
...
multiple
...
objects.
...
Failing
...
and
...
returning
...
somewhere
...
in
...
the
...
middle
...
of
...
this
...
function
...
without
...
freeing
...
all
...
of
...
the
...
allocated
...
memory
...
could
...
produce
...
a
...
memory
...
leak.
...
It
...
is
...
a
...
common
...
error
...
to
...
forget
...
to
...
free
...
one
...
(or
...
all)
...
of
...
the
...
objects
...
in
...
this
...
manner,
...
so
...
a
...
goto-chain
...
is
...
the
...
simplest
...
and
...
cleanest
...
way
...
to
...
organize
...
exits
...
when
...
order
...
is
...
preserved.
...
Noncompliant Code Example
| Code Block | ||
|---|---|---|
| ||
int Code Exampleint do_something(void){ // ... definitions ,,,... obj1 = malloc(...); if (!obj1){ Â returnreturn -1; } obj2 = malloc(...); if (!obj2){ free(obj1); return -1; } obj3 = malloc(...); if (!obj3){ free(obj2); return -1; // Forgot to free obj1 -- Memory leak } // ... more code ... } h2. Compliant Solutionint |
Notice how there is a memory leak if obj3 cannot be allocated. This is also just a small example; in much larger examples, errors like this would be even harder to detect. Hence, the goto-chain...
Compliant Solution
| Code Block | ||
|---|---|---|
| ||
int do_something(void){ // ... definitions ,,, obj1 = malloc(...); if (!obj1){ goto FAIL_OBJ1; } obj2 = malloc(...); if (!obj2){ goto FAIL_OBJ2; } obj3 = malloc(...); if (!obj3){ goto FAIL_OBJ3; } ? // ... more code ... FAIL_OBJ3: free(obj2); FAIL_OBJ2: free(obj1); FAIL_OBJ1: return -1; } |
This
...
code
...
is
...
guaranteed
...
to
...
clean
...
up
...
properly
...
whenever
...
an
...
allocation
...
fails.
...
It
...
is
...
cleaner
...
and
...
prevents
...
rewriting
...
of
...
similar
...
code
...
upon
...
every
...
function
...
error.