StringUtil::extractLine (#989)

* Added extractLine line parsing to StringUtil. Use for matching lines instead of calcLines. calcLines uses extractLine to extract lines.
Fixed problems found in output of some tests- due to how a how final line is handled. Now a final line has a \r or \n\r combination, but nothing else after it, it is considered the last line (not the line after it).

* Use StringUtil::extractLine in slang-generate.

* Improved comment on extractLine

* Remove test code from StringUtil::extractLine

* Made StringUtil::extractLine act as if line terminators are 'separators'.
Added unit-test-string.cpp - to check behavior.

* Adding LineParser - not entirely necessary, but slightly easier to use.

* Improved LineParser::Iterator end testing.
Added improved tests for LineParser.

* Move line comparson after termination case - to fix problem with gcc release build.

* Make UnownedStringSlice handle comparison when begin is nullptr - as it uses memcmp and passing nullptr to memcmp is undefined, leading to optimizer being able to do some unfortunate optimizations on gcc.

1 files changed, 19 insertions, 2 deletions

diff --git a/source/core/slang-string.h b/source/core/slang-string.h
index 4975e9ec6..8a9e83cd1 100644
--- a/source/core/slang-string.h
+++ b/source/core/slang-string.h
@@ -119,8 +119,25 @@ namespace Slang
 
         bool operator==(UnownedStringSlice const& other) const
         {
-            return size() == other.size()
-                && memcmp(begin(), other.begin(), size()) == 0;
+            // Note that memcmp is undefined when passed in null ptrs, so if we want to handle
+            // we need to cover that case.
+            // Can only be nullptr if size is 0.
+            auto thisSize = size();
+            auto otherSize = other.size();
+
+            if (thisSize != otherSize)
+            {
+                return false;
+            }
+
+            const char*const thisChars = begin();
+            const char*const otherChars = other.begin();
+            if (thisChars == otherChars || thisSize == 0)
+            {
+                return true;
+            }
+            SLANG_ASSERT(thisChars && otherChars);
+            return memcmp(thisChars, otherChars, thisSize) == 0;
         }
 
         bool operator==(char const* str) const