From d3eb902f7f45cc20b5802b2ef3c85b88fdec52c0 Mon Sep 17 00:00:00 2001 From: Siddhesh Poyarekar Date: Tue, 20 Feb 2018 11:11:31 +0000 Subject: [PATCH] c++: Fix spurious fallthrough warning on break The C++ frontend generates a break that results in the fallthrough warning misfiring in nested switch blocks where cases in the inner switch block return, rendering the break pointless. The fallthrough detection in finish_break_stmt does not work either because the condition is encoded as an IF_STMT and not a COND_EXPR. Fix this by adding a condition for IF_STMT in the langhooks.block_may_fallthru for C++. Fix tested on x86_64. gcc/cp * cp-objcp-common.c (cxx_block_may_fallthru): Add case for IF_STMT. gcc/testsuite * g++.dg/nested-switch.C: New test case. From-SVN: r257843 --- gcc/cp/ChangeLog | 5 +++ gcc/cp/cp-objcp-common.c | 5 +++ gcc/testsuite/ChangeLog | 4 +++ .../g++.dg/warn/Wimplicit-fallthrough-3.C | 31 +++++++++++++++++++ 4 files changed, 45 insertions(+) create mode 100644 gcc/testsuite/g++.dg/warn/Wimplicit-fallthrough-3.C diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog index f2bcce9784e1..dd408e0bf687 100644 --- a/gcc/cp/ChangeLog +++ b/gcc/cp/ChangeLog @@ -1,3 +1,8 @@ +2018-02-20 Siddhesh Poyarekar + + * cp-objcp-common.c (cxx_block_may_fallthru): Add case for + IF_STMT. + 2018-02-20 Paolo Carlini PR c++/84446 diff --git a/gcc/cp/cp-objcp-common.c b/gcc/cp/cp-objcp-common.c index a45dda4d012a..5289a89e4869 100644 --- a/gcc/cp/cp-objcp-common.c +++ b/gcc/cp/cp-objcp-common.c @@ -349,6 +349,11 @@ cxx_block_may_fallthru (const_tree stmt) case THROW_EXPR: return false; + case IF_STMT: + if (block_may_fallthru (THEN_CLAUSE (stmt))) + return true; + return block_may_fallthru (ELSE_CLAUSE (stmt)); + case SWITCH_STMT: return (!SWITCH_STMT_ALL_CASES_P (stmt) || !SWITCH_STMT_NO_BREAK_P (stmt) diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index 476374a2333e..cfae982f6942 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,7 @@ +2018-02-20 Siddhesh Poyarekar + + * g++.dg/warn/Wimplicit-fallthrough-3.C: New test case. + 2018-02-20 Martin Liska PR c/84310 diff --git a/gcc/testsuite/g++.dg/warn/Wimplicit-fallthrough-3.C b/gcc/testsuite/g++.dg/warn/Wimplicit-fallthrough-3.C new file mode 100644 index 000000000000..2f06817d9ee8 --- /dev/null +++ b/gcc/testsuite/g++.dg/warn/Wimplicit-fallthrough-3.C @@ -0,0 +1,31 @@ +// Verify that there are no spurious warnings in nested switch statements due +// to the unnecessary break in the inner switch block. +// { dg-do compile } +// { dg-options "-Wimplicit-fallthrough" } */ + +int +foo (int c1, int c2, int c3) +{ + switch (c2) + { + case 0: + switch (c3) // { dg-bogus "may fall through" } + { + case 0: + if (c1) + return 1; + else + return 2; + break; + + default: + return 3; + } + + case 1: + return 4; + default: + return 5; + break; + } +} -- 2.47.2