Move C interface from slang.h to slang-deprecated.h (#5301)

* Squash redundant move warnings

* Move C interface from slang.h to slang-deprecated.h

spGetBuildTagString remains, because it's useful to have before the
global session exists.

This C API is used quite pervasively in the C++ helpers (for example
slang::UserAttribute. It's not trivial to move these to
slang-deprecated.h as they're entangled with some enums which are
themselves used elsewhere in the compiler.

The fact that these helpers use the C API can be viewed as an
implementation detail for now, and this usage moved to slang-deprecated
in due course.

Closes https://github.com/shader-slang/slang/issues/4758

* Squash warnings for our usage of our deprecated API

---------

Co-authored-by: Yong He <yonghe@outlook.com>

3 files changed, 25 insertions, 3 deletions

diff --git a/source/core/slang-common.h b/source/core/slang-common.h
index 855ea08db..8c84894ca 100644
--- a/source/core/slang-common.h
+++ b/source/core/slang-common.h
@@ -181,6 +181,28 @@ public:
 #    define SLANG_EXHAUSTIVE_SWITCH_END
 #endif
 
+#if SLANG_GCC
+#    define SLANG_ALLOW_DEPRECATED_BEGIN \
+         _Pragma("GCC diagnostic push"); \
+         _Pragma("GCC diagnostic ignored \"-Wdeprecated-declarations\"");
+#    define SLANG_ALLOW_DEPRECATED_END \
+         _Pragma("GCC diagnostic pop");
+#elif SLANG_CLANG
+#    define SLANG_ALLOW_DEPRECATED_BEGIN \
+         _Pragma("clang diagnostic push"); \
+         _Pragma("clang diagnostic ignored \"-Wdeprecated-declarations\"");
+#    define SLANG_ALLOW_DEPRECATED_END \
+         _Pragma("clang diagnostic pop");
+#elif SLANG_VC
+#    define SLANG_ALLOW_DEPRECATED_BEGIN \
+        _Pragma("warning(push)"); \
+        _Pragma("warning(disable : 4996)");
+#    define SLANG_ALLOW_DEPRECATED_END \
+        _Pragma("warning(pop)");
+#else
+#    define SLANG_ALLOW_DEPRECATED_BEGIN
+#    define SLANG_ALLOW_DEPRECATED_END
+#endif
 
 //
 // Use `SLANG_ASSUME(myBoolExpression);` to inform the compiler that the condition is true.
diff --git a/source/core/slang-persistent-cache.cpp b/source/core/slang-persistent-cache.cpp
index d934d1b26..2b4113e16 100644
--- a/source/core/slang-persistent-cache.cpp
+++ b/source/core/slang-persistent-cache.cpp
@@ -226,7 +226,7 @@ String PersistentCache::getEntryFileName(const Key& key)
 {
     StringBuilder str;
     str << m_cacheDirectory << "/" << key.toString();
-    return std::move(str);
+    return str;
 }
 
 struct CacheIndexHeader
diff --git a/source/core/slang-string-util.cpp b/source/core/slang-string-util.cpp
index c7625e1e0..79f7307dc 100644
--- a/source/core/slang-string-util.cpp
+++ b/source/core/slang-string-util.cpp
@@ -332,7 +332,7 @@ UnownedStringSlice StringUtil::getAtInSplit(const UnownedStringSlice& in, char s
     append(format, args, builder);
     va_end(args);
 
-    return std::move(builder);
+    return builder;
 }
 
 /* static */UnownedStringSlice StringUtil::getSlice(ISlangBlob* blob)
@@ -384,7 +384,7 @@ ComPtr<ISlangBlob> StringUtil::createStringBlob(const String& string)
     }
 
     builder.appendInPlace(dstChars, numChars);
-    return std::move(builder);
+    return builder;
 }
 
 /* static */String StringUtil::calcCharReplaced(const String& string, char fromChar, char toChar)