* Catch SIGINT to terminate cleanly when the user tries to interrupt

  Nix.  This is to prevent Berkeley DB from becoming wedged.

  Unfortunately it is not possible to throw C++ exceptions from a
  signal handler.  In fact, you can't do much of anything except
  change variables of type `volatile sig_atomic_t'.  So we set an
  interrupt flag in the signal handler and check it at various
  strategic locations in the code (by calling checkInterrupt()).
  Since this is unlikely to cover all cases (e.g., (semi-)infinite
  loops), sometimes SIGTERM may now be required to kill Nix.

1 files changed, 17 insertions, 0 deletions

diff --git a/src/libutil/util.cc b/src/libutil/util.cc
index 28e276a32..5c8b7279c 100644
--- a/src/libutil/util.cc
+++ b/src/libutil/util.cc
@@ -132,6 +132,7 @@ Strings readDirectory(const Path & path)
 
     struct dirent * dirent;
     while (errno = 0, dirent = readdir(dir)) { /* sic */
+        checkInterrupt();
         string name = dirent->d_name;
         if (name == "." || name == "..") continue;
         names.push_back(name);
@@ -144,6 +145,8 @@ Strings readDirectory(const Path & path)
 
 void deletePath(const Path & path)
 {
+    checkInterrupt();
+
     printMsg(lvlVomit, format("deleting path `%1%'") % path);
 
     struct stat st;
@@ -170,6 +173,8 @@ void deletePath(const Path & path)
 
 void makePathReadOnly(const Path & path)
 {
+    checkInterrupt();
+
     struct stat st;
     if (lstat(path.c_str(), &st))
 	throw SysError(format("getting attributes of path `%1%'") % path);
@@ -199,6 +204,7 @@ static Path tempName()
 Path createTempDir()
 {
     while (1) {
+        checkInterrupt();
 	Path tmpDir = tempName();
 	if (mkdir(tmpDir.c_str(), 0777) == 0) return tmpDir;
 	if (errno != EEXIST)
@@ -246,6 +252,7 @@ void Nest::open(Verbosity level, const format & f)
 
 void printMsg_(Verbosity level, const format & f)
 {
+    checkInterrupt();
     if (level > verbosity) return;
     string spaces;
     for (int i = 0; i < nestingLevel; i++)
@@ -257,6 +264,7 @@ void printMsg_(Verbosity level, const format & f)
 void readFull(int fd, unsigned char * buf, size_t count)
 {
     while (count) {
+        checkInterrupt();
         ssize_t res = read(fd, (char *) buf, count);
         if (res == -1) throw SysError("reading from file");
         if (res == 0) throw Error("unexpected end-of-file");
@@ -269,6 +277,7 @@ void readFull(int fd, unsigned char * buf, size_t count)
 void writeFull(int fd, const unsigned char * buf, size_t count)
 {
     while (count) {
+        checkInterrupt();
         ssize_t res = write(fd, (char *) buf, count);
         if (res == -1) throw SysError("writing to file");
         count -= res;
@@ -344,3 +353,11 @@ AutoCloseDir::operator DIR *()
     return dir;
 }
 
+
+volatile sig_atomic_t _isInterrupted = 0;
+
+void _interrupted()
+{
+    _isInterrupted = 0;
+    throw Error("interrupted by the user");
+}