[flang-commits] [flang] [flang] Fix incorrect offset for zero-size COMMON block members. (PR #214174)

[Daniel Chen via flang-commits]

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@@ -0,0 +1,60 @@
+! RUN: %flang_fc1 -emit-hlfir -o - %s | FileCheck %s
+
+! Test that CHARACTER*0 symbols in a COMMON block are assigned their correct
+! sequential offset rather than always offset 0 (the block base address).
+!
+! Block /blk/ layout:
+!   offset  0 : ii1  (integer(8), 8 bytes)
+!   offset  8 : zc0  (character*0, 0 bytes)  <- zero-size, no storage consumed
+!   offset  8 : ll1  (integer(8), 8 bytes)
+!   Total: 16 bytes
+!
+! Before fix (compute-offsets.cpp): DoSymbol() returned early for zero-size
+! symbols without calling symbol.set_offset(), leaving zc0 stamped with
+! offset 0. This caused storage(%1[0]) for zc0 instead of storage(%1[8]).
+
+subroutine char0_common
+  integer(8) :: ii1
+  character*0 :: zc0
+  integer(8) :: ll1
+  common /blk/ ii1, zc0, ll1
+  call use(ii1, zc0, ll1)
+end subroutine
+
+! CHECK: fir.global common @blk_(dense<0> : vector<16xi8>) {alignment = 8 : i64} : !fir.array<16xi8>
+
+! CHECK-LABEL: func.func @_QPchar0_common
+
+! ii1 at offset 0
+! CHECK: %[[BASE:.*]] = fir.address_of(@blk_) : !fir.ref<!fir.array<16xi8>>
+! CHECK: hlfir.declare {{.*}} storage(%[[BASE]][0]) {uniq_name = "_QFchar0_commonEii1"}
+
+! ll1 at offset 8
+! CHECK: hlfir.declare {{.*}} storage(%[[BASE]][8]) {uniq_name = "_QFchar0_commonEll1"}
+
+! zc0 at offset 8 (not 0) -- key assertion
+! CHECK: hlfir.declare {{.*}} storage(%[[BASE]][8]) {uniq_name = "_QFchar0_commonEzc0"}
+
+! Test that a zero-size CHARACTER in a COMMON block does not trigger a false
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DanielCChen wrote:

I separated the tests.

https://github.com/llvm/llvm-project/pull/214174