Don't interpret strings as format strings

Ludo reported this error:

  unexpected Nix daemon error: boost::too_few_args: format-string refered to more arguments than were passed

coming from this line:

  printMsg(lvlError, run.program + ": " + string(err, 0, p));

The problem here is that the string ends up implicitly converted to a
Boost format() object, so % characters are treated specially.  I
always assumed (wrongly) that strings are converted to a format object
that outputs the string as-is.

Since this assumption appears in several places that may be hard to
grep for, I've added some C++ type hackery to ensures that the right
thing happens.  So you don't have to worry about % in statements like

  printMsg(lvlError, "foo: " + s);

or

  throw Error("foo: " + s);

1 files changed, 16 insertions, 7 deletions

diff --git a/src/libutil/types.hh b/src/libutil/types.hh
index a2ab1cc0ee83..4b5ce9a78c48 100644
--- a/src/libutil/types.hh
+++ b/src/libutil/types.hh
@@ -20,28 +20,37 @@ using std::vector;
 using boost::format;
 
 
+struct FormatOrString
+{
+    string s;
+    FormatOrString(const string & s) : s(s) { };
+    FormatOrString(const format & f) : s(f.str()) { };
+    FormatOrString(const char * s) : s(s) { };
+};
+
+
 /* BaseError should generally not be caught, as it has Interrupted as
    a subclass. Catch Error instead. */
-class BaseError : public std::exception 
+class BaseError : public std::exception
 {
 protected:
     string prefix_; // used for location traces etc.
     string err;
 public:
     unsigned int status; // exit status
-    BaseError(const format & f, unsigned int status = 1);
+    BaseError(const FormatOrString & fs, unsigned int status = 1);
     ~BaseError() throw () { };
     const char * what() const throw () { return err.c_str(); }
     const string & msg() const throw () { return err; }
     const string & prefix() const throw () { return prefix_; }
-    BaseError & addPrefix(const format & f);
+    BaseError & addPrefix(const FormatOrString & fs);
 };
 
 #define MakeError(newClass, superClass) \
     class newClass : public superClass                  \
     {                                                   \
     public:                                             \
-        newClass(const format & f, unsigned int status = 1) : superClass(f, status) { }; \
+        newClass(const FormatOrString & fs, unsigned int status = 1) : superClass(fs, status) { }; \
     };
 
 MakeError(Error, BaseError)
@@ -50,7 +59,7 @@ class SysError : public Error
 {
 public:
     int errNo;
-    SysError(const format & f);
+    SysError(const FormatOrString & fs);
 };
 
 
@@ -63,8 +72,8 @@ typedef string Path;
 typedef list<Path> Paths;
 typedef set<Path> PathSet;
 
- 
-typedef enum { 
+
+typedef enum {
     lvlError = 0,
     lvlInfo,
     lvlTalkative,