diff --git a/gcc/c-family/c-gimplify.cc b/gcc/c-family/c-gimplify.cc index 2f44e125f92..694ccf921a6 100644 --- a/gcc/c-family/c-gimplify.cc +++ b/gcc/c-family/c-gimplify.cc @@ -307,6 +307,27 @@ genericize_c_loop (tree *stmt_p, location_t start_locus, tree cond, tree body, } append_to_statement_list (body, &stmt_list); + if (c_dialect_cxx () + && stmt_list + && TREE_CODE (stmt_list) == STATEMENT_LIST) + { + tree_stmt_iterator tsi = tsi_last (stmt_list); + if (!tsi_end_p (tsi)) + { + tree t = *tsi; + while (TREE_CODE (t) == CLEANUP_POINT_EXPR + || TREE_CODE (t) == EXPR_STMT + || CONVERT_EXPR_CODE_P (TREE_CODE (t))) + t = TREE_OPERAND (t, 0); + /* For C++, if iteration statement body ends with fallthrough + statement, mark it such that we diagnose it even if next + statement would be labeled statement with case/default label. */ + if (TREE_CODE (t) == CALL_EXPR + && !CALL_EXPR_FN (t) + && CALL_EXPR_IFN (t) == IFN_FALLTHROUGH) + TREE_NOTHROW (t) = 1; + } + } finish_bc_block (&stmt_list, bc_continue, clab); if (incr) { diff --git a/gcc/gimple-walk.cc b/gcc/gimple-walk.cc index 9516d61ffa9..20df7e2d7e4 100644 --- a/gcc/gimple-walk.cc +++ b/gcc/gimple-walk.cc @@ -56,11 +56,21 @@ walk_gimple_seq_mod (gimple_seq *pseq, walk_stmt_fn callback_stmt, gcc_assert (wi); wi->callback_result = ret; - return wi->removed_stmt ? NULL : gsi_stmt (gsi); + gimple *g; + if (!wi->removed_stmt) + g = gsi_stmt (gsi); + else + { + g = NULL; + wi->removed_stmt = false; + } + return g; } if (!wi->removed_stmt) gsi_next (&gsi); + else + wi->removed_stmt = false; } if (wi) diff --git a/gcc/gimplify.cc b/gcc/gimplify.cc index 77f07af6ec5..d52d71b9b6b 100644 --- a/gcc/gimplify.cc +++ b/gcc/gimplify.cc @@ -2791,17 +2791,33 @@ expand_FALLTHROUGH_r (gimple_stmt_iterator *gsi_p, bool *handled_ops_p, *handled_ops_p = false; break; case GIMPLE_CALL: + static_cast(wi->info)[0] = UNKNOWN_LOCATION; if (gimple_call_internal_p (stmt, IFN_FALLTHROUGH)) { + location_t loc = gimple_location (stmt); gsi_remove (gsi_p, true); + wi->removed_stmt = true; + + /* nothrow flag is added by genericize_c_loop to mark fallthrough + statement at the end of some loop's body. Those should be + always diagnosed, either because they indeed don't precede + a case label or default label, or because the next statement + is not within the same iteration statement. */ + if ((stmt->subcode & GF_CALL_NOTHROW) != 0) + { + pedwarn (loc, 0, "attribute % not preceding " + "a case label or default label"); + break; + } + if (gsi_end_p (*gsi_p)) { - *static_cast(wi->info) = gimple_location (stmt); - return integer_zero_node; + static_cast(wi->info)[0] = BUILTINS_LOCATION; + static_cast(wi->info)[1] = loc; + break; } bool found = false; - location_t loc = gimple_location (stmt); gimple_stmt_iterator gsi2 = *gsi_p; stmt = gsi_stmt (gsi2); @@ -2851,6 +2867,7 @@ expand_FALLTHROUGH_r (gimple_stmt_iterator *gsi_p, bool *handled_ops_p, } break; default: + static_cast(wi->info)[0] = UNKNOWN_LOCATION; break; } return NULL_TREE; @@ -2862,14 +2879,16 @@ static void expand_FALLTHROUGH (gimple_seq *seq_p) { struct walk_stmt_info wi; - location_t loc; + location_t loc[2]; memset (&wi, 0, sizeof (wi)); - wi.info = (void *) &loc; + loc[0] = UNKNOWN_LOCATION; + loc[1] = UNKNOWN_LOCATION; + wi.info = (void *) &loc[0]; walk_gimple_seq_mod (seq_p, expand_FALLTHROUGH_r, NULL, &wi); - if (wi.callback_result == integer_zero_node) + if (loc[0] != UNKNOWN_LOCATION) /* We've found [[fallthrough]]; at the end of a switch, which the C++ standard says is ill-formed; see [dcl.attr.fallthrough]. */ - pedwarn (loc, 0, "attribute % not preceding " + pedwarn (loc[1], 0, "attribute % not preceding " "a case label or default label"); } diff --git a/gcc/internal-fn.def b/gcc/internal-fn.def index 319e0ab26cd..3d5aca0cddf 100644 --- a/gcc/internal-fn.def +++ b/gcc/internal-fn.def @@ -533,7 +533,9 @@ DEF_INTERNAL_FN (ATOMIC_AND_FETCH_CMP_0, ECF_LEAF, NULL) DEF_INTERNAL_FN (ATOMIC_OR_FETCH_CMP_0, ECF_LEAF, NULL) DEF_INTERNAL_FN (ATOMIC_XOR_FETCH_CMP_0, ECF_LEAF, NULL) -/* To implement [[fallthrough]]. */ +/* To implement [[fallthrough]]. If the TREE_NOTHROW or GF_CALL_NOTHROW flag + is set on the call (normally redundant with ECF_NOTHROW), it marks + [[fallthrough]] at the end of C++ loop body. */ DEF_INTERNAL_FN (FALLTHROUGH, ECF_LEAF | ECF_NOTHROW, NULL) /* To implement __builtin_launder. */ diff --git a/gcc/testsuite/g++.dg/DRs/dr2406.C b/gcc/testsuite/g++.dg/DRs/dr2406.C new file mode 100644 index 00000000000..856a1ea2f91 --- /dev/null +++ b/gcc/testsuite/g++.dg/DRs/dr2406.C @@ -0,0 +1,82 @@ +// DR 2406 - [[fallthrough]] attribute and iteration statements +// PR c++/107571 +// { dg-do compile { target c++11 } } +// { dg-options "-pedantic-errors -Wimplicit-fallthrough" } + +void bar (); +void baz (); +void qux (); + +void +foo (int n) +{ + switch (n) + { + case 1: + case 2: + bar (); + [[fallthrough]]; + case 3: + do + { + [[fallthrough]]; // { dg-error "attribute 'fallthrough' not preceding a case label or default label" } + } + while (false); + case 6: + do + { + [[fallthrough]]; // { dg-error "attribute 'fallthrough' not preceding a case label or default label" } + } + while (n--); + case 7: + while (false) + { + [[fallthrough]]; // { dg-error "attribute 'fallthrough' not preceding a case label or default label" } + } + case 5: + baz (); // { dg-warning "this statement may fall through" } + case 4: // { dg-message "here" } + qux (); + [[fallthrough]]; // { dg-error "attribute 'fallthrough' not preceding a case label or default label" } + } +} + +void +corge (int n) +{ + switch (n) + { + case 1: + { + int i = 0; + do + { + [[fallthrough]]; // { dg-error "attribute 'fallthrough' not preceding a case label or default label" } + } + while (false); + } + case 2: + bar (); + break; + default: + break; + } +} + +void +fred (int n) +{ + switch (n) + { + case 1: + { + int i = 0; + [[fallthrough]]; + } + case 2: + bar (); + break; + default: + break; + } +}