[Dependency Scanning] Add string dispose API to libSwiftScan interface

Author: artemcm

Sources/CSwiftScan/include/swiftscan_header.h

@@ -193,6 +193,8 @@ typedef struct {
 
   //=== Cleanup Functions ---------------------------------------------------===//
   void
+  (*swiftscan_string_dispose)(swiftscan_string_ref_t);
+  void
   (*swiftscan_string_set_dispose)(swiftscan_string_set_t *);
   void
   (*swiftscan_dependency_graph_dispose)(swiftscan_dependency_graph_t);

Sources/SwiftDriver/Jobs/PrintTargetInfoJob.swift

@@ -185,7 +185,8 @@ extension Driver {
     if let swiftScanLibPath = optionalSwiftScanLibPath,
        fileSystem.exists(swiftScanLibPath) {
       let libSwiftScanInstance = try SwiftScan(dylib: swiftScanLibPath)
-      if libSwiftScanInstance.canQueryTargetInfo() {
+      if libSwiftScanInstance.canQueryTargetInfo(),
+         libSwiftScanInstance.supportsStringDispose() {
         let targetInfoData = try libSwiftScanInstance.queryTargetInfoJSON(invocationCommand: invocationCommand)
         return try JSONDecoder().decode(FrontendTargetInfo.self, from: targetInfoData)
       }

Sources/SwiftDriver/SwiftScan/SwiftScan.swift

@@ -271,6 +271,10 @@ internal extension swiftscan_diagnostic_severity_t {
            api.swiftscan_diagnostic_get_severity != nil &&
            api.swiftscan_diagnostics_set_dispose != nil
   }
+
+  @_spi(Testing) public func supportsStringDispose() -> Bool {
+    return api.swiftscan_string_dispose != nil
+  }
 
   @_spi(Testing) public func queryScannerDiagnostics() throws -> [ScannerDiagnosticPayload] {
     var result: [ScannerDiagnosticPayload] = []
@@ -328,7 +332,9 @@ internal extension swiftscan_diagnostic_severity_t {
                                              Int32(invocationCommand.count),
                                              invocationStringArray)
     }
-    let targetInfoString = try toSwiftString(api.swiftscan_compiler_target_info_query(invocation))
+    let targetInfoStringRef = api.swiftscan_compiler_target_info_query(invocation)
+    defer { api.swiftscan_string_dispose(targetInfoStringRef) }
+    let targetInfoString = try toSwiftString(targetInfoStringRef)
     let targetInfoData = Data(targetInfoString.utf8)
     return targetInfoData
   }
@@ -395,6 +401,8 @@ private extension swiftscan_functions_t {
       try loadOptional("swiftscan_diagnostic_get_severity")
     self.swiftscan_diagnostics_set_dispose =
       try loadOptional("swiftscan_diagnostics_set_dispose")
+    self.swiftscan_string_dispose =
+      try loadOptional("swiftscan_string_dispose")
 
     // isFramework on binary module dependencies
     self.swiftscan_swift_binary_detail_get_is_framework =