Hi Tobias,
Am 13.12.22 um 22:41 schrieb Tobias Burnus:
Note: We only talk about those two functions, the other functions are used
by both GCC <= 11 and GCC >= 12.
yes.
Fortunately, these functions matter most as they map GFC internals to CFI
internals or vice versa. Most other functions are user callable and there
incompatibilities are less likely to show up and GCC 11 users also could
profit from fixes there. It looks as if CFI_section and CFI_select_part had
some larger changes, likewise CFI_setpointer.
Back to differences: 'diff -U0 -p -w' against the last GCC 11 branch shows:
...
@@ -35,0 +37,2 @@ export_proto(cfi_desc_to_gfc_desc);
+/* NOTE: Since GCC 12, the FE generates code to do the conversion
+ directly without calling this function. */
@@ -63 +66 @@ cfi_desc_to_gfc_desc (gfc_array_void *d,
- d->dtype.version = s->version;
+ d->dtype.version = 0;
I was wondering what the significance of "version" is.
In ISO_Fortran_binding.h we seem to always have
#define CFI_VERSION 1
and it did not change with gcc-12.
If it is just decoration (for now), then it is not important.
I just didn't see where it is used.
@@ -76,0 +80 @@ cfi_desc_to_gfc_desc (gfc_array_void *d,
+ if (GFC_DESCRIPTOR_DATA (d))
@@ -79,3 +83,7 @@ cfi_desc_to_gfc_desc (gfc_array_void *d,
- GFC_DESCRIPTOR_LBOUND(d, n) = (index_type)s->dim[n].lower_bound;
- GFC_DESCRIPTOR_UBOUND(d, n) = (index_type)(s->dim[n].extent
- + s->dim[n].lower_bound
- 1);
+ CFI_index_t lb = 1;
+
+ if (s->attribute != CFI_attribute_other)
+ lb = s->dim[n].lower_bound;
+
+ GFC_DESCRIPTOR_LBOUND(d, n) = (index_type)lb;
+ GFC_DESCRIPTOR_UBOUND(d, n) = (index_type)(s->dim[n].extent + lb
- 1);
Oh, now I see that on 11-branch in trans-expr.c we set a hard-coded
attribute = 2 instead of using CFI_attribute_other, even if that was
available as a macro defining the very same value. Thus it is ok.
@@ -89,0 +98,2 @@ export_proto(gfc_desc_to_cfi_desc);
+/* NOTE: Since GCC 12, the FE generates code to do the conversion
+ directly without calling this function. */
@@ -100,2 +110,2 @@ gfc_desc_to_cfi_desc (CFI_cdesc_t **d_pt
- d = malloc (sizeof (CFI_cdesc_t)
- + (CFI_type_t)(CFI_MAX_RANK * sizeof (CFI_dim_t)));
+ d = calloc (1, (sizeof (CFI_cdesc_t)
+ + (CFI_type_t)(CFI_MAX_RANK * sizeof (CFI_dim_t))));
@@ -107 +117 @@ gfc_desc_to_cfi_desc (CFI_cdesc_t **d_pt
- d->version = s->dtype.version;
+ d->version = CFI_VERSION;
This treatment of "version" was the equivalent to the above that
confused me. Assuming we were to change CFI_VERSION in gcc-13+,
is this the right choice here regarding backward compatibility?
Probably yes. I don't have a better suggestion. The problem is that it
usually only matters in some corner cases, like in the PR where a not
some argument is passed to the GFC→CFI conversion but first a Fortran
function is called with TYPE(*) any only then it is passed on. – Such
cases are usually not in the testsuite. (With GCC 12 we have a rather
complex testsuite, but obviously it also does not cover everything.)
Well, I understand we have to draw a line here, whether we
reproduce every bug in <= gcc-11 where the user may have
attempted to implement a workaround. That might be tough.
Well, in the real world there are larger installations with large
software stacks, and it is easier said to "compile each component
with the same compiler version" than done...
I concur – but there were really many fixes for the array descriptor /
TS29113 in GCC 12.
It is simply not possible to fix tons of bugs and be 100% compatible
with the working bits of the old version – especially if they only work
if one does not look sharply at the result. (Like here, were 'type' is
wrong, which does not matter unless in programs which use them.)
True. I was only thinking of the 90+ percent of valid and common
uses that we really consider important.
So besides the "version" question ok from my side.
Thanks,
Harald
Thanks,
Tobias
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