Fixed GCC mem-access warnings (#2565)

+ using "if defined" more consistently for Clang.

imgui.cpp

@@ -995,7 +995,7 @@ CODE
 #endif
 
 // Clang/GCC warnings with -Weverything
-#ifdef __clang__
+#if defined(__clang__)
 #pragma clang diagnostic ignored "-Wunknown-pragmas"        // warning : unknown warning group '-Wformat-pedantic *'        // not all warnings are known by all clang versions.. so ignoring warnings triggers new warnings on some configuration. great!
 #pragma clang diagnostic ignored "-Wold-style-cast"         // warning : use of old-style cast                              // yes, they are more terse.
 #pragma clang diagnostic ignored "-Wfloat-equal"            // warning : comparing floating point with == or != is unsafe   // storing and comparing against same constants (typically 0.0f) is ok.

imgui_demo.cpp

@@ -63,7 +63,7 @@ Index of this file:
 #ifdef _MSC_VER
 #pragma warning (disable: 4996) // 'This function or variable may be unsafe': strcpy, strdup, sprintf, vsnprintf, sscanf, fopen
 #endif
-#ifdef __clang__
+#if defined(__clang__)
 #pragma clang diagnostic ignored "-Wold-style-cast"             // warning : use of old-style cast                              // yes, they are more terse.
 #pragma clang diagnostic ignored "-Wdeprecated-declarations"    // warning : 'xx' is deprecated: The POSIX name for this item.. // for strdup used in demo code (so user can copy & paste the code)
 #pragma clang diagnostic ignored "-Wint-to-void-pointer-cast"   // warning : cast to 'void *' from smaller integer type 'int'

imgui_draw.cpp

@@ -52,7 +52,7 @@ Index of this file:
 #endif
 
 // Clang/GCC warnings with -Weverything
-#ifdef __clang__
+#if defined(__clang__)
 #pragma clang diagnostic ignored "-Wold-style-cast"         // warning : use of old-style cast                              // yes, they are more terse.
 #pragma clang diagnostic ignored "-Wfloat-equal"            // warning : comparing floating point with == or != is unsafe   // storing and comparing against same constants ok.
 #pragma clang diagnostic ignored "-Wglobal-constructors"    // warning : declaration requires a global destructor           // similar to above, not sure what the exact difference is.
@@ -100,7 +100,7 @@ namespace IMGUI_STB_NAMESPACE
 #pragma warning (disable: 4456)                             // declaration of 'xx' hides previous local declaration
 #endif
 
-#ifdef __clang__
+#if defined(__clang__)
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wunused-function"
 #pragma clang diagnostic ignored "-Wmissing-prototypes"
@@ -108,7 +108,7 @@ namespace IMGUI_STB_NAMESPACE
 #pragma clang diagnostic ignored "-Wcast-qual"              // warning : cast from 'const xxxx *' to 'xxx *' drops const qualifier //
 #endif
 
-#ifdef __GNUC__
+#if defined(__GNUC__)
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wtype-limits"              // warning: comparison is always true due to limited range of data type [-Wtype-limits]
 #pragma GCC diagnostic ignored "-Wcast-qual"                // warning: cast from type 'const xxxx *' to type 'xxxx *' casts away qualifiers
@@ -151,15 +151,15 @@ namespace IMGUI_STB_NAMESPACE
 #endif
 #endif
 
-#ifdef __GNUC__
+#if defined(__GNUC__)
 #pragma GCC diagnostic pop
 #endif
 
-#ifdef __clang__
+#if defined(__clang__)
 #pragma clang diagnostic pop
 #endif
 
-#ifdef _MSC_VER
+#if defined(_MSC_VER)
 #pragma warning (pop)
 #endif
 

imgui_internal.h

@@ -36,15 +36,17 @@ Index of this file:
 #include <math.h>       // sqrtf, fabsf, fmodf, powf, floorf, ceilf, cosf, sinf
 #include <limits.h>     // INT_MIN, INT_MAX
 
+// Visual Studio warnings
 #ifdef _MSC_VER
 #pragma warning (push)
 #pragma warning (disable: 4251) // class 'xxx' needs to have dll-interface to be used by clients of struct 'xxx' // when IMGUI_API is set to__declspec(dllexport)
 #endif
 
-#ifdef __clang__
+// Clang/GCC warnings with -Weverything
+#if defined(__clang__)
 #pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Wunused-function"                // for stb_textedit.h
-#pragma clang diagnostic ignored "-Wmissing-prototypes"             // for stb_textedit.h
+#pragma clang diagnostic ignored "-Wunused-function"        // for stb_textedit.h
+#pragma clang diagnostic ignored "-Wmissing-prototypes"     // for stb_textedit.h
 #pragma clang diagnostic ignored "-Wold-style-cast"
 #if __has_warning("-Wzero-as-null-pointer-constant")
 #pragma clang diagnostic ignored "-Wzero-as-null-pointer-constant"
@@ -52,6 +54,11 @@ Index of this file:
 #if __has_warning("-Wdouble-promotion")
 #pragma clang diagnostic ignored "-Wdouble-promotion"
 #endif
+#elif defined(__GNUC__)
+#pragma GCC diagnostic push
+#if __GNUC__ >= 8
+#pragma GCC diagnostic ignored "-Wclass-memaccess"          // warning: 'memset/memcpy' clearing/writing an object of type 'xxxx' with no trivial copy-assignment; use assignment or value-initialization instead
+#endif
 #endif
 
 //-----------------------------------------------------------------------------
@@ -1645,8 +1652,10 @@ extern void                 ImGuiTestEngineHook_ItemInfo(ImGuiContext* ctx, ImGu
 #define IMGUI_TEST_ENGINE_ITEM_INFO(_ID, _LABEL, _FLAGS)  do { } while (0)
 #endif
 
-#ifdef __clang__
+#if defined(__clang__)
 #pragma clang diagnostic pop
+#elif defined(__GNUC__)
+#pragma GCC diagnostic pop
 #endif
 
 #ifdef _MSC_VER

imgui_widgets.cpp

@@ -51,7 +51,7 @@ Index of this file:
 #endif
 
 // Clang/GCC warnings with -Weverything
-#ifdef __clang__
+#if defined(__clang__)
 #pragma clang diagnostic ignored "-Wold-style-cast"         // warning : use of old-style cast                              // yes, they are more terse.
 #pragma clang diagnostic ignored "-Wfloat-equal"            // warning : comparing floating point with == or != is unsafe   // storing and comparing against same constants (typically 0.0f) is ok.
 #pragma clang diagnostic ignored "-Wformat-nonliteral"      // warning : format string is not a string literal              // passing non-literal to vsnformat(). yes, user passing incorrect format strings can crash the code.