add clang diagnostic pragmas to quiet unreachable-code warnings

fixes: #486

4 files changed, 16 insertions, 2 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index f889f985..6ac0c7f1 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -510,6 +510,7 @@ if(CMAKE_COMPILER_IS_GNUCC OR "${CMAKE_C_COMPILER_ID}" MATCHES "Clang")
   check_c_compiler_flag(-Wsizeof-pointer-memaccess HAVE_GCC_POINTER_MEMACCESS)
   check_c_compiler_flag(-Wformat-security HAVE_GCC_FORMAT_SECURITY)
   check_c_compiler_flag(-Wredundant-decls HAVE_GCC_REDUNDANT_DECLS)
+  check_c_compiler_flag(-Wunreachable-code HAVE_GCC_UNREACHABLE_CODE)
   set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fvisibility=hidden -Wno-deprecated -Wall -Wno-unknown-pragmas -Wextra -Winit-self -Wunused -Wno-div-by-zero -Wundef -Wpointer-arith -Wtype-limits -Wwrite-strings -Werror=return-type")
   if(HAVE_GCC_UNUSED_BUT_SET)
     set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wunused-but-set-variable")
@@ -526,6 +527,9 @@ if(CMAKE_COMPILER_IS_GNUCC OR "${CMAKE_C_COMPILER_ID}" MATCHES "Clang")
   if(HAVE_GCC_REDUNDANT_DECLS)
     set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wredundant-decls")
   endif()
+  if(HAVE_GCC_UNREACHABLE_CODE)
+    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wunreachable-code")
+  endif()
   if(CMAKE_SYSTEM_NAME MATCHES Linux OR CMAKE_SYSTEM_NAME STREQUAL GNU)
     set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -D_XOPEN_SOURCE=500 -D_DEFAULT_SOURCE -D_GNU_SOURCE")
   endif()
@@ -542,6 +546,7 @@ if(CMAKE_COMPILER_IS_GNUCXX OR "${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
   check_cxx_compiler_flag(-Wreorder HAVE_GXX_REORDER)
   check_cxx_compiler_flag(-Wformat-security HAVE_GXX_FORMAT_SECURITY)
   check_cxx_compiler_flag(-Wredundant-decls HAVE_GXX_REDUNDANT_DECLS)
+  check_cxx_compiler_flag(-Wunreachable-code HAVE_GXX_UNREACHABLE_CODE)
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fvisibility=hidden -Weffc++ -Wno-deprecated -Wall -Wextra -Woverloaded-virtual -Winit-self -Wunused -Wno-div-by-zero -Wundef -Wpointer-arith -Wtype-limits -Wwrite-strings -Werror=return-type")
   if(HAVE_GXX_UNUSED_BUT_SET)
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wunused-but-set-variable")
@@ -561,6 +566,9 @@ if(CMAKE_COMPILER_IS_GNUCXX OR "${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
   if(HAVE_GXX_REDUNDANT_DECLS)
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wredundant-decls")
   endif()
+  if(HAVE_GXX_UNREACHABLE_CODE)
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wunreachable-code")
+  endif()
   if(CMAKE_SYSTEM_NAME MATCHES Linux OR CMAKE_SYSTEM_NAME STREQUAL GNU)
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -D_XOPEN_SOURCE=500 -D_DEFAULT_SOURCE -D_GNU_SOURCE")
   endif()
diff --git a/ReleaseNotes.txt b/ReleaseNotes.txt
index 11ceac75..98826346 100644
--- a/ReleaseNotes.txt
+++ b/ReleaseNotes.txt
@@ -10,6 +10,7 @@ Version 3.0.15 (UNRELEASED):
  * Fix x-property comma handling and escaping
  * Built-in timezones updated to tzdata2022d (now with a VTIMEZONE for each time zone alias)
  * Fix fuzzer issues
+ * Handle unreachable-code compile warnings with clang
 
 Version 3.0.14 (05 February 2022):
 ----------------------------------
diff --git a/src/libicalss/icalssyacc.c b/src/libicalss/icalssyacc.c
index 2416e528..e386ad80 100644
--- a/src/libicalss/icalssyacc.c
+++ b/src/libicalss/icalssyacc.c
@@ -1599,9 +1599,11 @@ yyerrorlab:
   /* Pacify compilers like GCC when the user code never invokes
      YYERROR and the label yyerrorlab therefore never appears in user
      code.  */
-  if (/*CONSTCOND*/ 0)
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunreachable-code"
+    if (/*CONSTCOND*/ 0)
      goto yyerrorlab;
-
+#pragma clang diagnostic pop
   /* Do not reclaim the symbols of the rule which action triggered
      this YYERROR.  */
   YYPOPSTACK (yylen);
diff --git a/src/test/regression-storage.c b/src/test/regression-storage.c
index 7ce594d2..eb11f6d5 100644
--- a/src/test/regression-storage.c
+++ b/src/test/regression-storage.c
@@ -305,6 +305,8 @@ void test_bdbset()
 
     return;     // for now... TODO fix these broken tests..
 
+#pragma clang diagnostic push /* remove when/if we remove the proceeding return statement */
+#pragma clang diagnostic ignored "-Wunreachable-code"
     start = icaltime_from_timet_with_zone(time(0), 0, NULL);
     end = start;
     end.hour++;
@@ -452,6 +454,7 @@ void test_bdbset()
         }
         icalset_free(cout);
     }
+#pragma clang diagnostic pop
 }
 
 #endif