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Don't interpret strings as format strings

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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);
This commit is contained in:
Eelco Dolstra 2014-03-28 16:59:26 +01:00
parent 24cb65efc3
commit 49009573bc
3 changed files with 32 additions and 23 deletions
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23
src/libutil/types.hh
View file

@ -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,