Vader's death wasn't canonically confirmed in the film, nor in the original novelisation which was released several weeks before the film came out (and which, in turn is based on the final draft shooting script).
When we last see him (in both the film and the novel) he's blasting off into deep space.
To the other side, Darth Vader’s fighter began spinning helplessly.
Unimpressed by the Dark Lord’s desperate glower, various controls and
instruments gave back readings which were brutally truthful.
Completely out of control, the tiny ship continued spinning in the
opposite direction from the destroyed wingman—out into the endless
reaches of deep space.
Purely for your interest the last draft script in which he died was the 2nd draft (which, incidentally is the first in which he appears).
He survived in the 4th Draft
CU. Vader. The impact of the collision throws Vader out of control and creates havoc on his control board. He looks around frantically trying to salvage his situation.
237. EXT. SPACE AROUND THE DEATH STAR: Full Shot of Vader’s ship spinning out of control with a bent solar fin, heading for deep space.
He survived (probably) in the 3rd Draft
226-227. INT. VADER IMPERIAL TIE FIGHTER – COCKPIT – TRAVELING
Vader’s starship with a bent solar fin limps into the vast darkness of space attempting to make it back to the relative safety of Alderaan.
He died in the 2nd Draft (in a suicide run on Han Solo's ship)
Vader’s starship swoops down on the battered pirate ship, unleashing a
heavy barrage of laser bolts. Chewbacca in the rear gun turret blazes
away at the Sith starship. One of Vader’s huge solar fins breaks up,
but the Black Knight manages to keep the disabled craft on course and
crash dives into the pirate craft, exploding on impact.