4 files changed, 37 insertions, 20 deletions

diff --git a/src/libexpr/eval-cache.cc b/src/libexpr/eval-cache.cc
index f26e6d724..5969ee449 100644
--- a/src/libexpr/eval-cache.cc
+++ b/src/libexpr/eval-cache.cc
@@ -576,8 +576,9 @@ std::string AttrCursor::getString()
 
     auto & v = forceValue();
 
-    if (v.type() != nString && v.type() != nPath)
-        root->state.error<TypeError>("'%s' is not a string but %s", getAttrPathStr()).debugThrow();
+    if (v.type() != nString && v.type() != nPath) {
+        root->state.error<TypeError>("'%s' is not a string but %s", getAttrPathStr(), v.type()).debugThrow();
+    }
 
     return v.type() == nString ? v.string.s : v.path().to_string();
 }
@@ -622,11 +623,11 @@ string_t AttrCursor::getStringWithContext()
         NixStringContext context;
         copyContext(v, context);
         return {v.string.s, std::move(context)};
-    }
-    else if (v.type() == nPath)
+    } else if (v.type() == nPath) {
         return {v.path().to_string(), {}};
-    else
-        root->state.error<TypeError>("'%s' is not a string but %s", getAttrPathStr()).debugThrow();
+    } else {
+        root->state.error<TypeError>("'%s' is not a string but %s", getAttrPathStr(), v.type()).debugThrow();
+    }
 }
 
 bool AttrCursor::getBool()
diff --git a/src/libstore/build/derivation-goal.cc b/src/libstore/build/derivation-goal.cc
index f879a580e..faebd3c43 100644
--- a/src/libstore/build/derivation-goal.cc
+++ b/src/libstore/build/derivation-goal.cc
@@ -1009,7 +1009,7 @@ void DerivationGoal::buildDone()
             if (diskFull)
                 msg += "\nnote: build failure may have been caused by lack of free disk space";
 
-            throw BuildError(msg);
+            throw BuildError("%s", msg);
         }
 
         /* Compute the FS closure of the outputs and register them as
diff --git a/src/libstore/path.cc b/src/libstore/path.cc
index c896ff927..2f929b7b3 100644
--- a/src/libstore/path.cc
+++ b/src/libstore/path.cc
@@ -64,6 +64,11 @@ StorePath Store::parseStorePath(std::string_view path) const
 
 std::optional<StorePath> Store::maybeParseStorePath(std::string_view path) const
 {
+    // If it's not an absolute path, or if the dirname of the path isn't /nix/store
+    // (or whatever our storeDir is), then it can't be a store path.
+    if ((path.size() > 0 && path[0] != '/') || dirOf(canonPath(path)) != this->storeDir) {
+        return std::nullopt;
+    }
     try {
         return parseStorePath(path);
     } catch (Error &) {
diff --git a/src/libutil/fmt.hh b/src/libutil/fmt.hh
index c68591b72..aa7c6926a 100644
--- a/src/libutil/fmt.hh
+++ b/src/libutil/fmt.hh
@@ -1,8 +1,15 @@
 #pragma once
 ///@file
 
-#include <boost/format.hpp>
+#include <iostream>
 #include <string>
+#include <optional>
+#include <boost/format.hpp>
+// Darwin stdenv does not define _GNU_SOURCE but does have _Unwind_Backtrace.
+#ifdef __APPLE__
+#define BOOST_STACKTRACE_GNU_SOURCE_NOT_REQUIRED
+#endif
+#include <boost/stacktrace.hpp>
 #include "ansicolor.hh"
 
 namespace nix {
@@ -157,23 +164,27 @@ public:
      */
     template<typename... Args>
     HintFmt(const std::string & format, const Args &... args)
-        : HintFmt(boost::format(format), args...)
-    {
-    }
-
-    HintFmt(const HintFmt & hf) : fmt(hf.fmt) {}
-
-    template<typename... Args>
-    HintFmt(boost::format && fmt, const Args &... args)
-        : fmt(fmt_internal::HintFmt(std::move(fmt), args...).into_format())
+        // Note the function try block.
+        try : fmt(fmt_internal::HintFmt(boost::format(format), args...).into_format())
     {
         if (this->fmt.remaining_args() != 0) {
-            throw boost::io::too_few_args(
-                this->fmt.bound_args() + this->fmt.fed_args(), this->fmt.expected_args()
-            );
+            // Abort. I don't want anything to catch this, I want a coredump.
+            std::cerr << "HintFmt received incorrect number of format args. Original format string: '";
+            std::cerr << format << "'; number of arguments: " << sizeof...(args) << "\n";
+            // And regardless of the coredump give me a damn stacktrace.
+            std::cerr << boost::stacktrace::stacktrace() << std::endl;
+            abort();
         }
+    } catch (boost::io::format_error & ex) {
+        // Same thing, but for anything that happens in the member initializers.
+        std::cerr << "HintFmt received incorrect format string. Original format string: '";
+        std::cerr << format << "'; number of arguments: " << sizeof...(args) << "\n";
+        std::cerr << boost::stacktrace::stacktrace() << std::endl;
+        abort();
     }
 
+    HintFmt(const HintFmt & hf) : fmt(hf.fmt) {}
+
     std::string str() const
     {
         return fmt.str();