Various bug fixes (#778)

zencore fixes:
- filesystem.cpp: ReadFile error reporting logic
- compactbinaryvalue.h: CbValue::As*String error reporting logic

zenhttp fixes:
- httpasio BindAcceptor would `return 0;` in a function returning `std::string` (UB)
- httpsys async workpool initialization race

zenstore fixes:
- cas.cpp: GetFileCasResults Results param passed by value instead of reference (large chunk results were silently lost)
- structuredcachestore.cpp: MissCount unconditionally incremented (counted hits as misses)
- cacherpc.cpp: Wrong boolean in Incomplete response array (all entries marked incomplete)
- cachedisklayer.cpp: sizeof(sizeof(...)) in two validation checks computed sizeof(size_t) instead of struct size
- buildstore.cpp: Wrong hash tracked in GC key list (BlobHash pushed twice instead of MetadataHash)
- buildstore.cpp: Removed duplicate m_LastAccessTimeUpdateCount increment in PutBlob

zenserver fixes:
- httpbuildstore.cpp: Reversed subtraction in HTTP range calculation (unsigned underflow)
- hubservice.cpp: Deadlock in Provision() calling Wake() while holding m_Lock (extracted WakeLocked helper)
- zipfs.cpp: Data race in GetFile() lazy initialization (added RwLock with shared/exclusive paths)

1 files changed, 2 insertions, 2 deletions

diff --git a/src/zenhttp/servers/httpasio.cpp b/src/zenhttp/servers/httpasio.cpp
index 1c0ebef90..fbc7fe401 100644
--- a/src/zenhttp/servers/httpasio.cpp
+++ b/src/zenhttp/servers/httpasio.cpp
@@ -89,10 +89,10 @@ IsIPv6AvailableSysctl(void)
 		char buf[16];
 		if (fgets(buf, sizeof(buf), f))
 		{
-			fclose(f);
 			// 0 means IPv6 enabled, 1 means disabled
 			val = atoi(buf);
 		}
+		fclose(f);
 	}
 
 	return val == 0;
@@ -1544,7 +1544,7 @@ struct HttpAcceptor
 		{
 			ZEN_WARN("Unable to initialize asio service, (bind returned '{}')", BindErrorCode.message());
 
-			return 0;
+			return {};
 		}
 
 		if (EffectivePort != BasePort)