Explicitly set CMAKE_XXX_FLAGS_DEBUG

Explicitly set the C/C++ CMake Debug flags (CMAKE_C_FLAGS_DEBUG /
CMAKE_CXX_FLAGS_DEBUG) for all supported compilers, with optimization
disabled. This allows us to use this variable to selectively force
Debug flags (i.e. optimization off) for selected targets, such as unit
tests.

Change-Id: Iaafc3d8c8b289fa49105780944f71a890ce95edc
Reviewed-on: http://review.couchbase.org/55457
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>

cmake/Modules/CouchbaseClangOptions.cmake

@@ -8,6 +8,7 @@ SET(CB_CLANG_LANG_VER "-std=gnu99")
 # Release, only differing in whether debugging information is enabled.
 SET(CMAKE_C_FLAGS_RELEASE        "-O3 -DNDEBUG")
 SET(CMAKE_C_FLAGS_RELWITHDEBINFO "-O3 -DNDEBUG -g")
+SET(CMAKE_C_FLAGS_DEBUG          "-O0 -g")
 
 IF ("${ENABLE_WERROR}" STREQUAL "YES")
    SET(CB_CLANG_WERROR "-Werror")

cmake/Modules/CouchbaseClangxxOptions.cmake

@@ -7,6 +7,7 @@ SET(CB_CLANGXX_THREAD "-pthread")
 # Release, only differing in whether debugging information is enabled.
 SET(CMAKE_CXX_FLAGS_RELEASE        "-O3 -DNDEBUG")
 SET(CMAKE_CXX_FLAGS_RELWITHDEBINFO "-O3 -DNDEBUG -g")
+SET(CMAKE_CXX_FLAGS_DEBUG          "-O0 -g")
 
 IF ("${ENABLE_WERROR}" STREQUAL "YES")
    SET(CB_CLANGXX_WERROR "-Werror")

cmake/Modules/CouchbaseGccOptions.cmake

@@ -8,6 +8,7 @@ SET(CB_GNU_LANG_VER "-std=gnu99")
 # Release, only differing in whether debugging information is enabled.
 SET(CMAKE_C_FLAGS_RELEASE        "-O3 -DNDEBUG")
 SET(CMAKE_C_FLAGS_RELWITHDEBINFO "-O3 -DNDEBUG -g")
+SET(CMAKE_C_FLAGS_DEBUG          "-O0 -g")
 
 IF ("${ENABLE_WERROR}" STREQUAL "YES")
    SET(CB_GNU_WERROR "-Werror")

cmake/Modules/CouchbaseGxxOptions.cmake

@@ -7,6 +7,7 @@ SET(CB_GXX_THREAD "-pthread")
 # Release, only differing in whether debugging information is enabled.
 SET(CMAKE_CXX_FLAGS_RELEASE        "-O3 -DNDEBUG")
 SET(CMAKE_CXX_FLAGS_RELWITHDEBINFO "-O3 -DNDEBUG -g")
+SET(CMAKE_CXX_FLAGS_DEBUG          "-O0 -g")
 
 IF ("${ENABLE_WERROR}" STREQUAL "YES")
    SET(CB_GXX_WERROR "-Werror")

cmake/Modules/CouchbaseMsvcOptions.cmake

@@ -11,6 +11,7 @@ ENDIF()
 # Release, only differing in whether debugging information is enabled.
 SET(CMAKE_C_FLAGS_RELEASE        "/MD /O2 /Ob2 /D NDEBUG")
 SET(CMAKE_C_FLAGS_RELWITHDEBINFO "/MD /O2 /Ob2 /D NDEBUG /Zi")
+SET(CMAKE_C_FLAGS_DEBUG          "/MD /Od /Ob0 /Zi")
 
 SET(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${CB_MSVC_DEBUG} ${CB_MSVC_WARNINGS} ${CB_MSVC_VISIBILITY} ${CB_MSVC_THREAD} ${CB_MSVC_WERROR}")
 SET(CMAKE_LINK_FLAGS "${CMAKE_LINK_FLAGS} ${CB_MSVC_LDFLAGS}")

cmake/Modules/CouchbaseMsvcxxOptions.cmake

@@ -11,6 +11,7 @@ ENDIF()
 # Release, only differing in whether debugging information is enabled.
 SET(CMAKE_CXX_FLAGS_RELEASE        "/MD /O2 /Ob2 /D NDEBUG")
 SET(CMAKE_CXX_FLAGS_RELWITHDEBINFO "/MD /O2 /Ob2 /D NDEBUG /Zi")
+SET(CMAKE_CXX_FLAGS_DEBUG          "/MD /Od /Ob0 /Zi")
 
 # C++11 support has gradually increased in MSVC starting with 2010 (v16), but
 # we declare that at least VS 2013 (v18) is needed for std::atomic / C99.

cmake/Modules/README.md

@@ -0,0 +1,39 @@
+# CMake modules
+
+Some brief description / explanation of the use of certain files and
+variables.
+
+
+## CouchbaseXXX.cmake files
+
+These files are used to define Couchbase-specific macros and
+variables. For example, they define the the various compiler flags for
+each supported compiler, supported memory allocator options, etc.
+
+### Couchbase<Compiler>Options.cmake
+
+These files define the default compilation flags for each of the
+various supported compilers.
+
+Descriptions of specific variables of interest:
+
+* CMAKE_CXX_FLAGS_RELEASE / CMAKE_CXX_FLAGS_RELWITH_DEBINFO: Compiler
+  flags for Release and RelWIthDebInfo builds. Note that as of 4.0 we
+  actually ship a RelWithDebInfo build (to maximise our ability to
+  debug issues from the field) and hence
+  CMAKE_CXX_FLAGS_RELWITH_DEBINFO are overridden to be as optimized
+  as the normal Release flags, but keeping debug enabled.
+
+* CMAKE_CXX_FLAGS_DEBUG: Compiler flags for Debug builds. We override
+  this to explicitly set Debug to have Optimization disabled (by
+  default it just uses the implicit default). This allows us to use
+  this variable to selectively force Debug flags (i.e. optimization
+  off) for selected targets, such as unit tests.
+
+
+## FindCouchbaseXXX.cmake files
+
+These files are similar to the standard CMake FindXXX.cmake files,
+except Couchbase-specific files. The main purpose of the 'Couchbase'
+prefix is just to make it obvious which are ours and which are
+standard when used.