Merge pull request #11618 from NixOS/ignoreException-interrupt

Split ignoreException for destructors vs interrupt-safe

src/libutil/current-process.cc

@@ -45,7 +45,7 @@ unsigned int getMaxCPU()
         auto period = cpuMaxParts[1];
         if (quota != "max")
                 return std::ceil(std::stoi(quota) / std::stof(period));
-    } catch (Error &) { ignoreException(lvlDebug); }
+    } catch (Error &) { ignoreExceptionInDestructor(lvlDebug); }
     #endif
 
     return 0;

src/libutil/file-descriptor.cc

@@ -2,6 +2,7 @@
 #include "signals.hh"
 #include "finally.hh"
 #include "serialise.hh"
+#include "util.hh"
 
 #include <fcntl.h>
 #include <unistd.h>
@@ -65,7 +66,7 @@ AutoCloseFD::~AutoCloseFD()
     try {
         close();
     } catch (...) {
-        ignoreException();
+        ignoreExceptionInDestructor();
     }
 }
 

src/libutil/file-system.cc

@@ -5,6 +5,7 @@
 #include "signals.hh"
 #include "finally.hh"
 #include "serialise.hh"
+#include "util.hh"
 
 #include <atomic>
 #include <cerrno>
@@ -517,7 +518,7 @@ AutoDelete::~AutoDelete()
             }
         }
     } catch (...) {
-        ignoreException();
+        ignoreExceptionInDestructor();
     }
 }
 

src/libutil/logging.cc

@@ -346,7 +346,7 @@ Activity::~Activity()
     try {
         logger.stopActivity(id);
     } catch (...) {
-        ignoreException();
+        ignoreExceptionInDestructor();
     }
 }
 

src/libutil/serialise.cc

@@ -1,5 +1,6 @@
 #include "serialise.hh"
 #include "signals.hh"
+#include "util.hh"
 
 #include <cstring>
 #include <cerrno>
@@ -52,7 +53,7 @@ void BufferedSink::flush()
 
 FdSink::~FdSink()
 {
-    try { flush(); } catch (...) { ignoreException(); }
+    try { flush(); } catch (...) { ignoreExceptionInDestructor(); }
 }
 
 

src/libutil/serialise.hh

@@ -503,7 +503,7 @@ struct FramedSource : Source
                 }
             }
         } catch (...) {
-            ignoreException();
+            ignoreExceptionInDestructor();
         }
     }
 
@@ -550,7 +550,7 @@ struct FramedSink : nix::BufferedSink
             to << 0;
             to.flush();
         } catch (...) {
-            ignoreException();
+            ignoreExceptionInDestructor();
         }
     }
 

src/libutil/thread-pool.cc

@@ -111,9 +111,8 @@ void ThreadPool::doWork(bool mainThread)
                         try {
                             std::rethrow_exception(exc);
                         } catch (std::exception & e) {
-                            if (!dynamic_cast<Interrupted*>(&e) &&
-                                !dynamic_cast<ThreadPoolShutDown*>(&e))
-                                ignoreException();
+                            if (!dynamic_cast<ThreadPoolShutDown*>(&e))
+                                ignoreExceptionExceptInterrupt();
                         } catch (...) {
                         }
                     }

src/libutil/unix/signals.cc

@@ -91,7 +91,7 @@ void unix::triggerInterrupt()
             try {
                 callback();
             } catch (...) {
-                ignoreException();
+                ignoreExceptionInDestructor();
             }
         }
     }

src/libutil/util.cc

@@ -1,6 +1,7 @@
 #include "util.hh"
 #include "fmt.hh"
 #include "file-path.hh"
+#include "signals.hh"
 
 #include <array>
 #include <cctype>
@@ -182,7 +183,7 @@ std::string shellEscape(const std::string_view s)
 }
 
 
-void ignoreException(Verbosity lvl)
+void ignoreExceptionInDestructor(Verbosity lvl)
 {
     /* Make sure no exceptions leave this function.
        printError() also throws when remote is closed. */
@@ -195,6 +196,17 @@ void ignoreException(Verbosity lvl)
     } catch (...) { }
 }
 
+void ignoreExceptionExceptInterrupt(Verbosity lvl)
+{
+    try {
+        throw;
+    } catch (const Interrupted & e) {
+        throw;
+    } catch (std::exception & e) {
+        printMsg(lvl, "error (ignored): %1%", e.what());
+    }
+}
+
 
 constexpr char base64Chars[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 

src/libutil/util.hh

@@ -156,9 +156,26 @@ std::string toLower(std::string s);
 std::string shellEscape(const std::string_view s);
 
 
-/* Exception handling in destructors: print an error message, then
-   ignore the exception. */
-void ignoreException(Verbosity lvl = lvlError);
+/**
+ * Exception handling in destructors: print an error message, then
+ * ignore the exception.
+ *
+ * If you're not in a destructor, you usually want to use `ignoreExceptionExceptInterrupt()`.
+ *
+ * This function might also be used in callbacks whose caller may not handle exceptions,
+ * but ideally we propagate the exception using an exception_ptr in such cases.
+ * See e.g. `PackBuilderContext`
+ */
+void ignoreExceptionInDestructor(Verbosity lvl = lvlError);
+
+/**
+ * Not destructor-safe.
+ * Print an error message, then ignore the exception.
+ * If the exception is an `Interrupted` exception, rethrow it.
+ *
+ * This may be used in a few places where Interrupt can't happen, but that's ok.
+ */
+void ignoreExceptionExceptInterrupt(Verbosity lvl = lvlError);