error: allow context to be added to Exception objects

PiperOrigin-RevId: 590237148
Change-Id: Ia4c7c4b3514fa6330288e2075724399f99286ef5

3 files changed, 10 insertions, 4 deletions

diff --git a/error.h b/error.h
index 6eed80e..5ca6c57 100644
--- a/error.h
+++ b/error.h
@@ -32,14 +32,20 @@ namespace stg {
 
 class Exception : public std::exception {
  public:
-  explicit Exception(const std::string& message) : message_(message) {}
+  explicit Exception(const std::string& message) {
+    Add(message);
+  }
 
   const char* what() const noexcept(true) final {
     return message_.c_str();
   }
 
+  void Add(const std::string& message) {
+    (message_ += message) += '\n';
+  }
+
  private:
-  const std::string message_;
+  std::string message_;
 };
 
 class Check {
diff --git a/stg.cc b/stg.cc
index 8776d39..82a372e 100644
--- a/stg.cc
+++ b/stg.cc
@@ -234,7 +234,7 @@ int main(int argc, char* argv[]) {
     }
     return 0;
   } catch (const stg::Exception& e) {
-    std::cerr << e.what() << '\n';
+    std::cerr << e.what();
     return 1;
   }
 }
diff --git a/stgdiff.cc b/stgdiff.cc
index 51dda88..18cc733 100644
--- a/stgdiff.cc
+++ b/stgdiff.cc
@@ -270,7 +270,7 @@ int main(int argc, char* argv[]) {
     }
     return status;
   } catch (const stg::Exception& e) {
-    std::cerr << e.what() << '\n';
+    std::cerr << e.what();
     return 1;
   }
 }