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From Martin Sebor <>
Subject Re: test for 21.strings.capacity
Date Sat, 04 Mar 2006 22:07:05 GMT
Anton Pevtsov wrote:
> The attached file contains the test for the basic_string methods
> described in 21.strings.capacity.
> Here the same to 27.stringbuf.virtuals schema is used. But I think we
> need to implement our own allocator class for the test purposes to
> strictly test some methods (max_size, capacity). Also may be useful to
> develop some analogue of the algorithms tests X class to be used instead
> of char and wchar_t (according to the standard here may be any POD
> type). Martin, what do you think about this?

I agree. Exercising the template with user-defined template arguments
in addition to the default ones is important. The header file named
mychar.h contains a user-defined character type and traits class that
was designed for this purpose. The header myallocator.h defines
a custom allocator that we could use. We need to port these headers
to the new driver first (it should be pretty easy). I also want to
rename them to follow the rw_xxx.h convention.

I made a few improvements to the test and committed it here:

My comments are below.

Btw., I noticed a bug in the test I decided not to fix and let you
do it :) The hardocded strings containing embedded NULs do not always
seem to be handled correctly (with my changes in place you will see
it if you run the test with the --trace option). The string object
needs to be initialized using the two-argument ctor.


> int traits_eof = -1;

This shouldn't be necessary. AFAIK, basic_string doesn't use EOF for

> template <class charT>
> struct CharTraits: std::char_traits<charT>
> {
>     typedef std::char_traits<charT> Base;
>     typedef typename Base::int_type int_type;

I think it would be useful to change the int_type here from the default,
say to short or something unusual.

>     // override eof() to detect bad assumptions
>     static int_type eof () { return traits_eof; }
>     static int_type not_eof (int_type c) {
>         return c == eof () ? int_type (!c) : c;
>     }

This shouldn't be necessary. As I mentioned above, basic_string doesn't
make use of these functions (they're good for I/O).

> };
> /**************************************************************************/
> struct VFun
> {
>     enum charT { Char, WChar };
>     enum Traits { DefaultTraits, UserTraits };
>     enum VirtualTag {
>         // which virtual function to exercise

Since (unlike basic_stringbuf) basic_string has no virtual functions
I changed the name of the class and of the tag to make more sense.

>         size, resize, length, reserve, capacity, max_size, clear, empty
>     };
> template <class charT>
> void widen (charT *buf, const char *str)

This function will need to take an additional argument -- the length
of string -- to correctly handle embedded NULs.

>     rw_assert (should_throw == ex_thrown, 0, line,
>                "line %d. basic_string<%s, %s, %s>.resize(%zu%{?}, %#c%{;}) "
>                "on \"%s\" should throw == %b, was thrown == %b",
>                __LINE__, pfid->cname_, pfid->tname_, "std::allocator",
>                nparam, resize2args, chart_param, 0 != str ? str : "<empty>",
>                should_throw, ex_thrown);

I changed this and the other statements to use the %{#*S} directive
designed for the formatting of generic basic_string objects. Check
it out, it's quite handy (so handy, in fact, that it exposed the
bug I mentioned above).

>     // check the results
>     static charT wstr_tmp [long_string_len];
>     widen (wstr_tmp, str);

When str contains embedded NULs they are not handled.

> void test_size (VFun *pfid)
> {
>     rw_info (0, 0, 0, "basic_string<%s, %s, %s>::size ()",
>              pfid->cname_, pfid->tname_, "std::allocator");
>     pfid->vfun_ = VFun::size;

I decided to move this assignment up to the caller for simplicity.

> #define TEST(str, size)                                                    \
>     test_string_capacity (pfid, __LINE__, str, sizeof str - 1,             \
>                           0, 0, size, false)

I think it's better (less error-prone) to #undef the macro just before
#defining it so I moved the #undef directives immediately above the


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