MacOS built: add workaround for missing view() member of std::ostringstream

src/libcmd/repl.cc

@@ -645,7 +645,7 @@ ProcessLineResult NixRepl::processLine(std::string line)
 
             logger->cout(trim(renderMarkdownToTerminal(markdown)));
         } else if (fallbackPos) {
-            std::stringstream ss;
+            std::ostringstream ss;
             ss << "Attribute `" << fallbackName << "`\n\n";
             ss << "  … defined at " << state->positions[fallbackPos] << "\n\n";
             if (fallbackDoc) {
@@ -654,7 +654,7 @@ ProcessLineResult NixRepl::processLine(std::string line)
                 ss << "No documentation found.\n\n";
             }
 
-            auto markdown = ss.view();
+            auto markdown = toView(ss);
             logger->cout(trim(renderMarkdownToTerminal(markdown)));
 
         } else

src/libexpr/eval.cc

@@ -539,7 +539,7 @@ std::optional<EvalState::Doc> EvalState::getDoc(Value & v)
     if (v.isLambda()) {
         auto exprLambda = v.payload.lambda.fun;
 
-        std::stringstream s(std::ios_base::out);
+        std::ostringstream s(std::ios_base::out);
         std::string name;
         auto pos = positions[exprLambda->getPos()];
         std::string docStr;
@@ -578,7 +578,7 @@ 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(s.view()), // NOTE: memory leak when compiled without GC
+            .doc = makeImmutableString(toView(s)), // NOTE: memory leak when compiled without GC
         };
     }
     if (isFunctor(v)) {
@@ -1804,7 +1804,7 @@ 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 = out.view();
+        auto exprStr = toView(out);
 
         if (auto eq = dynamic_cast<ExprOpEq *>(cond)) {
             try {

src/libexpr/primops.cc

@@ -2136,7 +2136,7 @@ static void prim_toXML(EvalState & state, const PosIdx pos, Value * * args, Valu
     std::ostringstream out;
     NixStringContext context;
     printValueAsXML(state, true, false, *args[0], out, context, pos);
-    v.mkString(out.view(), context);
+    v.mkString(toView(out), context);
 }
 
 static RegisterPrimOp primop_toXML({
@@ -2244,7 +2244,7 @@ static void prim_toJSON(EvalState & state, const PosIdx pos, Value * * args, Val
     std::ostringstream out;
     NixStringContext context;
     printValueAsJSON(state, true, *args[0], pos, out, context);
-    v.mkString(out.view(), context);
+    v.mkString(toView(out), context);
 }
 
 static RegisterPrimOp primop_toJSON({

src/libexpr/primops/fromTOML.cc

@@ -66,7 +66,7 @@ static void prim_fromTOML(EvalState & state, const PosIdx pos, Value * * args, V
                         attrs.alloc("_type").mkString("timestamp");
                         std::ostringstream s;
                         s << t;
-                        attrs.alloc("value").mkString(s.view());
+                        attrs.alloc("value").mkString(toView(s));
                         v.mkAttrs(attrs);
                     } else {
                         throw std::runtime_error("Dates and times are not supported");

src/libexpr/print.cc

@@ -460,7 +460,7 @@ private:
 
                 std::ostringstream s;
                 s << state.positions[v.payload.lambda.fun->pos];
-                output << " @ " << filterANSIEscapes(s.view());
+                output << " @ " << filterANSIEscapes(toView(s));
             }
         } else if (v.isPrimOp()) {
             if (v.primOp())

src/libstore/daemon.cc

@@ -94,7 +94,7 @@ struct TunnelLogger : public Logger
         showErrorInfo(oss, ei, false);
 
         StringSink buf;
-        buf << STDERR_NEXT << oss.view();
+        buf << STDERR_NEXT << toView(oss);
         enqueueMsg(buf.s);
     }
 

src/libutil/strings.cc

@@ -6,6 +6,21 @@
 
 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)};
+    }
+};
+
+std::string_view toView(const std::ostringstream & os)
+{
+    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 std::set<std::string> tokenizeString(std::string_view s, std::string_view separators);
 template std::vector<std::string> tokenizeString(std::string_view s, std::string_view separators);

src/libutil/strings.hh

@@ -8,6 +8,11 @@
 
 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/nix-build/nix-build.cc

@@ -260,9 +260,9 @@ static void main_nix_build(int argc, char * * argv)
                 // read the shebang to understand which packages to read from. Since
                 // this is handled via nix-shell -p, we wrap our ruby script execution
                 // in ruby -e 'load' which ignores the shebangs.
-                envCommand = fmt("exec %1% %2% -e 'load(ARGV.shift)' -- %3% %4%", execArgs, interpreter, shellEscape(script), joined.view());
+                envCommand = fmt("exec %1% %2% -e 'load(ARGV.shift)' -- %3% %4%", execArgs, interpreter, shellEscape(script), toView(joined));
             } else {
-                envCommand = fmt("exec %1% %2% %3% %4%", execArgs, interpreter, shellEscape(script), joined.view());
+                envCommand = fmt("exec %1% %2% %3% %4%", execArgs, interpreter, shellEscape(script), toView(joined));
             }
         }
 

src/nix-env/user-env.cc

@@ -111,7 +111,7 @@ bool createUserEnv(EvalState & state, PackageInfos & elems,
     auto manifestFile = ({
         std::ostringstream str;
         printAmbiguous(manifest, state.symbols, str, nullptr, std::numeric_limits<int>::max());
-        StringSource source { str.view() };
+        StringSource source { toView(str) };
         state.store->addToStoreFromDump(
             source, "env-manifest.nix", FileSerialisationMethod::Flat, ContentAddressMethod::Raw::Text, HashAlgorithm::SHA256, references);
     });

src/nix/config-check.cc

@@ -87,11 +87,11 @@ struct CmdConfigCheck : StoreCommand
         }
 
         if (dirs.size() != 1) {
-            std::stringstream ss;
+            std::ostringstream ss;
             ss << "Multiple versions of nix found in PATH:\n";
             for (auto & dir : dirs)
                 ss << "  " << dir << "\n";
-            return checkFail(ss.view());
+            return checkFail(toView(ss));
         }
 
         return checkPass("PATH contains only one nix version.");
@@ -125,14 +125,14 @@ struct CmdConfigCheck : StoreCommand
         }
 
         if (!dirs.empty()) {
-            std::stringstream ss;
+            std::ostringstream ss;
             ss << "Found profiles outside of " << settings.nixStateDir << "/profiles.\n"
                << "The generation this profile points to might not have a gcroot and could be\n"
                << "garbage collected, resulting in broken symlinks.\n\n";
             for (auto & dir : dirs)
                 ss << "  " << dir << "\n";
             ss << "\n";
-            return checkFail(ss.view());
+            return checkFail(toView(ss));
         }
 
         return checkPass("All profiles are gcroots.");
@@ -145,13 +145,13 @@ struct CmdConfigCheck : StoreCommand
             : PROTOCOL_VERSION;
 
         if (clientProto != storeProto) {
-            std::stringstream ss;
+            std::ostringstream ss;
             ss << "Warning: protocol version of this client does not match the store.\n"
                << "While this is not necessarily a problem it's recommended to keep the client in\n"
                << "sync with the daemon.\n\n"
                << "Client protocol: " << formatProtocol(clientProto) << "\n"
                << "Store protocol: " << formatProtocol(storeProto) << "\n\n";
-            return checkFail(ss.view());
+            return checkFail(toView(ss));
         }
 
         return checkPass("Client protocol matches store protocol.");