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Explain frag alignment hacks

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"the weird alignment hackery" comment doesn't help anyone understand
the code.  Explain what is going on.  Replace the zero length
obstack_alloc with obstack_finish, which by inspection of obstack.h is
all the zero length alloc does.

	* frags.c (frag_alloc): Comment.  Replace zero length
	obstack_alloc with obstack_finish.
	(frag_new): Remove unnecessary obstack_finish.
	* write.c (compress_frag, compress_debug): Likewise.
This commit is contained in:
Alan Modra
2025-09-03 09:50:17 +09:30
parent 11e5824cda
commit fcd717899e
2 changed files with 9 additions and 11 deletions
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14
gas/frags.c
View File

@@ -69,8 +69,8 @@ frag_alloc_check (const struct obstack *ob)
}
/* Allocate a frag on the specified obstack.
Call this routine from everywhere else, so that all the weird alignment
hackery can be done in just one place. */
Call this routine every time a new frag is made, so that the
alignment hackery can be done in just one place. */
fragS *
frag_alloc (struct obstack *ob, size_t extra)
@@ -78,7 +78,12 @@ frag_alloc (struct obstack *ob, size_t extra)
fragS *ptr;
int oalign;
(void) obstack_alloc (ob, 0);
/* This will align the obstack so the next struct we allocate on it
will begin at a correct boundary. */
(void) obstack_finish (ob);
/* Turn off alignment as otherwise obstack_alloc will align the end
of the frag (obstack next_free pointer), making it seem like the
frag already has contents in fr_literal. */
oalign = obstack_alignment_mask (ob);
obstack_alignment_mask (ob) = 0;
ptr = obstack_alloc (ob, extra + SIZEOF_STRUCT_FRAG);
@@ -172,9 +177,6 @@ frag_new (size_t old_frags_var_max_size
/* Make sure its type is valid. */
gas_assert (frag_now->fr_type != 0);
/* This will align the obstack so the next struct we allocate on it
will begin at a correct boundary. */
obstack_finish (&frchain_now->frch_obstack);
frchP = frchain_now;
know (frchP);
former_last_fragP = frchP->frch_last;

6
gas/write.c
View File

@@ -1456,7 +1456,6 @@ compress_frag (bool use_zstd, void *ctx, const char *contents, int in_size,
avail_out = obstack_room (ob);
if (avail_out <= 0)
{
obstack_finish (ob);
f = frag_alloc (ob, 0);
f->fr_type = rs_fill;
(*last_newf)->fr_next = f;
@@ -1570,10 +1569,7 @@ compress_debug (bfd *abfd, asection *sec, void *xxx ATTRIBUTE_UNUSED)
avail_out = obstack_room (ob);
if (avail_out <= 0)
{
fragS *newf;
obstack_finish (ob);
newf = frag_alloc (ob, 0);
fragS *newf = frag_alloc (ob, 0);
newf->fr_type = rs_fill;
last_newf->fr_next = newf;
last_newf = newf;