treewide: Remove toView() because it leads to segfaults when compiled…

src/libcmd/repl.cc

@@ -669,7 +669,7 @@ ProcessLineResult NixRepl::processLine(std::string line)
                 ss << "No documentation found.\n\n";
             }
 
-            auto markdown = toView(ss);
+            auto markdown = ss.view();
             logger->cout(trim(renderMarkdownToTerminal(markdown)));
 
         } else

src/libexpr/eval.cc

@@ -591,7 +591,7 @@ std::optional<EvalState::Doc> EvalState::getDoc(Value & v)
             .name = name,
             .arity = 0, // FIXME: figure out how deep by syntax only? It's not semantically useful though...
             .args = {},
-            .doc = makeImmutableString(toView(s)), // NOTE: memory leak when compiled without GC
+            .doc = makeImmutableString(s.view()), // NOTE: memory leak when compiled without GC
         };
     }
     if (isFunctor(v)) {
@@ -1811,7 +1811,7 @@ void ExprAssert::eval(EvalState & state, Env & env, Value & v)
     if (!state.evalBool(env, cond, pos, "in the condition of the assert statement")) {
         std::ostringstream out;
         cond->show(state.symbols, out);
-        auto exprStr = toView(out);
+        auto exprStr = out.view();
 
         if (auto eq = dynamic_cast<ExprOpEq *>(cond)) {
             try {

src/libexpr/primops.cc

@@ -2412,7 +2412,7 @@ static void prim_toXML(EvalState & state, const PosIdx pos, Value ** args, Value
     std::ostringstream out;
     NixStringContext context;
     printValueAsXML(state, true, false, *args[0], out, context, pos);
-    v.mkString(toView(out), context);
+    v.mkString(out.view(), context);
 }
 
 static RegisterPrimOp primop_toXML({
@@ -2520,7 +2520,7 @@ static void prim_toJSON(EvalState & state, const PosIdx pos, Value ** args, Valu
     std::ostringstream out;
     NixStringContext context;
     printValueAsJSON(state, true, *args[0], pos, out, context);
-    v.mkString(toView(out), context);
+    v.mkString(out.view(), context);
 }
 
 static RegisterPrimOp primop_toJSON({

src/libexpr/primops/fromTOML.cc

@@ -139,7 +139,7 @@ static void prim_fromTOML(EvalState & state, const PosIdx pos, Value ** args, Va
                 attrs.alloc("_type").mkStringNoCopy("timestamp");
                 std::ostringstream s;
                 s << t;
-                auto str = toView(s);
+                auto str = s.view();
                 forceNoNullByte(str);
                 attrs.alloc("value").mkString(str);
                 v.mkAttrs(attrs);

src/libexpr/print.cc

@@ -461,7 +461,7 @@ class Printer
 
                 std::ostringstream s;
                 s << state.positions[v.lambda().fun->pos];
-                output << " @ " << filterANSIEscapes(toView(s));
+                output << " @ " << filterANSIEscapes(s.view());
             }
         } else if (v.isPrimOp()) {
             if (v.primOp())

src/libmain/progress-bar.cc

@@ -183,7 +183,7 @@ class ProgressBar : public Logger
         std::ostringstream oss;
         showErrorInfo(oss, ei, loggerSettings.showTrace.get());
 
-        log(*state, ei.level, toView(oss));
+        log(*state, ei.level, oss.view());
     }
 
     void log(State & state, Verbosity lvl, std::string_view s)

src/libstore/daemon.cc

@@ -102,7 +102,7 @@ struct TunnelLogger : public Logger
         showErrorInfo(oss, ei, false);
 
         StringSink buf;
-        buf << STDERR_NEXT << toView(oss);
+        buf << STDERR_NEXT << oss.view();
         enqueueMsg(buf.s);
     }
 

src/libutil/include/nix/util/strings.hh

@@ -12,11 +12,6 @@
 
 namespace nix {
 
-/*
- * workaround for unavailable view() method (C++20) of std::ostringstream under MacOS with clang-16
- */
-std::string_view toView(const std::ostringstream & os);
-
 /**
  * String tokenizer.
  *

src/libutil/logging.cc

@@ -121,7 +121,7 @@ class SimpleLogger : public Logger
         std::ostringstream oss;
         showErrorInfo(oss, ei, loggerSettings.showTrace.get());
 
-        log(ei.level, toView(oss));
+        log(ei.level, oss.view());
     }
 
     void startActivity(

src/libutil/strings.cc

@@ -8,23 +8,6 @@
 
 namespace nix {
 
-struct view_stringbuf : public std::stringbuf
-{
-    inline std::string_view toView()
-    {
-        auto begin = pbase();
-        return {begin, begin + pubseekoff(0, std::ios_base::cur, std::ios_base::out)};
-    }
-};
-
-__attribute__((no_sanitize("undefined"))) std::string_view toView(const std::ostringstream & os)
-{
-    /* Downcasting like this is very much undefined behavior, so we disable
-       UBSAN for this function. */
-    auto buf = static_cast<view_stringbuf *>(os.rdbuf());
-    return buf->toView();
-}
-
 template std::list<std::string> tokenizeString(std::string_view s, std::string_view separators);
 template StringSet tokenizeString(std::string_view s, std::string_view separators);
 template std::vector<std::string> tokenizeString(std::string_view s, std::string_view separators);

src/nix/config-check.cc

@@ -100,7 +100,7 @@ struct CmdConfigCheck : StoreCommand
             ss << "Multiple versions of nix found in PATH:\n";
             for (auto & dir : dirs)
                 ss << "  " << dir << "\n";
-            return checkFail(toView(ss));
+            return checkFail(ss.view());
         }
 
         return checkPass("PATH contains only one nix version.");
@@ -143,7 +143,7 @@ struct CmdConfigCheck : StoreCommand
             for (auto & dir : dirs)
                 ss << "  " << dir << "\n";
             ss << "\n";
-            return checkFail(toView(ss));
+            return checkFail(ss.view());
         }
 
         return checkPass("All profiles are gcroots.");
@@ -162,7 +162,7 @@ struct CmdConfigCheck : StoreCommand
                << "sync with the daemon.\n\n"
                << "Client protocol: " << formatProtocol(clientProto) << "\n"
                << "Store protocol: " << formatProtocol(storeProto) << "\n\n";
-            return checkFail(toView(ss));
+            return checkFail(ss.view());
         }
 
         return checkPass("Client protocol matches store protocol.");

src/nix/nix-build/nix-build.cc

@@ -285,10 +285,10 @@ static void main_nix_build(int argc, char ** argv)
                         execArgs,
                         interpreter,
                         escapeShellArgAlways(script),
-                        toView(joined));
+                        joined.view());
             } else {
                 envCommand =
-                    fmt("exec %1% %2% %3% %4%", execArgs, interpreter, escapeShellArgAlways(script), toView(joined));
+                    fmt("exec %1% %2% %3% %4%", execArgs, interpreter, escapeShellArgAlways(script), joined.view());
             }
         }
 

src/nix/nix-env/user-env.cc

@@ -108,7 +108,7 @@ bool createUserEnv(
     auto manifestFile = ({
         std::ostringstream str;
         printAmbiguous(manifest, state.symbols, str, nullptr, std::numeric_limits<int>::max());
-        StringSource source{toView(str)};
+        StringSource source{str.view()};
         state.store->addToStoreFromDump(
             source,
             "env-manifest.nix",