Don't catch exceptions by value

(cherry picked from commit 893be6f5e36abb58bbaa9c49055a5218114dd514)
(cherry picked from commit bd79c1f6f6391786772a8a79962abe22f374cca4)

2 files changed, 3 insertions, 3 deletions

diff --git a/src/libexpr/json-to-value.cc b/src/libexpr/json-to-value.cc
index 3f6017957782..8bae986f97fc 100644
--- a/src/libexpr/json-to-value.cc
+++ b/src/libexpr/json-to-value.cc
@@ -111,9 +111,9 @@ static void parseJSON(EvalState & state, const char * & s, Value & v)
                 mkFloat(v, stod(tmp_number));
             else
                 mkInt(v, stol(tmp_number));
-        } catch (std::invalid_argument e) {
+        } catch (std::invalid_argument & e) {
             throw JSONParseError("invalid JSON number");
-        } catch (std::out_of_range e) {
+        } catch (std::out_of_range & e) {
             throw JSONParseError("out-of-range JSON number");
         }
     }
diff --git a/src/libexpr/primops/fetchGit.cc b/src/libexpr/primops/fetchGit.cc
index 6229fef8d02e..90f600284b22 100644
--- a/src/libexpr/primops/fetchGit.cc
+++ b/src/libexpr/primops/fetchGit.cc
@@ -38,7 +38,7 @@ GitInfo exportGit(ref<Store> store, const std::string & uri,
 
         try {
             runProgram("git", true, { "-C", uri, "diff-index", "--quiet", "HEAD", "--" });
-        } catch (ExecError e) {
+        } catch (ExecError & e) {
             if (!WIFEXITED(e.status) || WEXITSTATUS(e.status) != 1) throw;
             clean = false;
         }