Issue 2250: Follow-up On Library Issue 2207

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2250. Follow-up On Library Issue 2207

Section: 22.9.2.2 [bitset.cons], 22.9.2.3 [bitset.members], 27.4.3.3 [string.cons], 27.4.3.7 [string.modifiers], 27.4.3.8 [string.ops] Status: C++17 Submitter: Frank Birbacher Opened: 2013-04-18 Last modified: 2017-07-30

Priority: 3

View all other issues in [bitset.cons].

View all issues with C++17 status.

Discussion:

Similar to LWG 2207⁽ⁱ⁾ there are several other places where the "Requires" clause precludes the "Throws" condition. Searching for the out_of_range exception to be thrown, the following have been found (based on the working draft N3485):

22.9.2.2 [bitset.cons] p3+4
22.9.2.3 [bitset.members] p13+14 (set)
22.9.2.3 [bitset.members] p19+20 (reset)
22.9.2.3 [bitset.members] p27+28 (flip)
22.9.2.3 [bitset.members] p41+42 (test)
27.4.3.3 [string.cons] p3+4
27.4.3.7.2 [string.append] p3+4
27.4.3.7.3 [string.assign] p4+5
27.4.3.7.4 [string.insert] p1+2, p5+6, p9+10 (partially)
27.4.3.7.5 [string.erase] p1+2
27.4.3.7.6 [string.replace] p1+2, p5+6, p9+10 (partially)
27.4.3.7.7 [string.copy] p1+2
27.4.3.8.3 [string.substr] p1+2

[2013-10-15: Daniel provides wording]

In addition to the examples mentioned in the discussion, a similar defect exists for thread's join() and detach functions (see 32.4.3.6 [thread.thread.member]). The suggested wording applies a similar fix for these as well.

[2015-05, Lenexa]

STL : likes it
DK : does it change behavior?
Multiple : no
Move to ready? Unanimous

Proposed resolution:

This wording is relative to N3936.

Modify 22.9.2.2 [bitset.cons] as indicated: [Editorial comment: The wording form used to ammend the Throws element is borrowed from a similar style used in 27.4.3.7.6 [string.replace] p10]
```
template <class charT, class traits, class Allocator>
explicit
bitset(const basic_string<charT, traits, Allocator>& str,
       typename basic_string<charT, traits, Allocator>::size_type pos = 0,
       typename basic_string<charT, traits, Allocator>::size_type n =
         basic_string<charT, traits, Allocator>::npos,
         charT zero = charT('0'), charT one = charT('1'));
```
~~-3- Requires: pos <= str.size().~~
-4- Throws: out_of_range if pos > str.size() or invalid_argument if an invalid character is found (see below).
-5- Effects: Determines the effective length rlen of the initializing string as the smaller of n and str.size() - pos.
The function then throws invalid_argument if any of the rlen characters in str beginning at position pos is other than zero or one. The function uses traits::eq() to compare the character values.
[…]
Modify 22.9.2.3 [bitset.members] as indicated:
```
bitset<N>& set(size_t pos, bool val = true);
```
~~-13- Requires: pos is valid~~
-14- Throws: out_of_range if pos does not correspond to a valid bit position.
[…]
```
bitset<N>& reset(size_t pos);
```
~~-19- Requires: pos is valid~~
-20- Throws: out_of_range if pos does not correspond to a valid bit position.
[…]
```
bitset<N>& flip(size_t pos);
```
~~-27- Requires: pos is valid~~
-28- Throws: out_of_range if pos does not correspond to a valid bit position.
[…]
```
bool test(size_t pos) const;
```
~~-41- Requires: pos is valid~~
-42- Throws: out_of_range if pos does not correspond to a valid bit position.
[…]

Modify 27.4.3.3 [string.cons] as indicated:

basic_string(const basic_string& str,
             size_type pos, size_type n = npos,
             const Allocator& a = Allocator());
~~-3- Requires: pos <= str.size()~~
-4- Throws: out_of_range if pos > str.size().

Modify 27.4.3.5 [string.capacity] as indicated:
```
void resize(size_type n, charT c);
```
~~-6- Requires: n <= max_size()~~
-7- Throws: length_error if n > max_size().
Modify 27.4.3.7.2 [string.append] as indicated:
```
basic_string&
  append(const basic_string& str, size_type pos, size_type n = npos);
```
~~-3- Requires: pos <= str.size()~~
-4- Throws: out_of_range if pos > str.size().
Modify 27.4.3.7.3 [string.assign] as indicated:
```
basic_string&
  assign(const basic_string& str, size_type pos, 
         size_type n = npos);
```
~~-5- Requires: pos <= str.size()~~
-6- Throws: out_of_range if pos > str.size().
Modify 27.4.3.7.4 [string.insert] as indicated: [Editorial note: The first change suggestion is also a bug fix of the current wording, because (a) the function has parameter pos1 but the semantics refers to pos and (b) it is possible that this function can throw length_error, see p10]
```
basic_string&
  insert(size_type pos1, const basic_string& str);
```
~~-1- Requires: pos <= size().~~
~~-2- Throws: out_of_range if pos > size().~~
-3- Effects: ~~Calls~~Equivalent to: return insert(pos, str.data(), str.size());.
~~-4- Returns: *this.~~
```
basic_string&
  insert(size_type pos1, const basic_string& str,
         size_type pos2, size_type n = npos);
```
~~-5- Requires: pos1 <= size() and pos2 <= str.size().~~
-6- Throws: out_of_range if pos1 > size() or pos2 > str.size().
[…]
```
basic_string&
  insert(size_type pos, const charT* s, size_type n);
```
-9- Requires: s points to an array of at least n elements of charT ~~and pos <= size()~~.
-10- Throws: out_of_range if pos > size() or length_error if size() + n > max_size().
[…]
```
basic_string&
  insert(size_type pos, const charT* s);
```
-13- Requires: ~~pos <= size() and~~ s points to an array of at least traits::length(s) + 1 elements of charT.
-14- Effects: Equivalent to return insert(pos, s, traits::length(s));.
~~-15- Returns: *this.~~
Modify 27.4.3.7.5 [string.erase] as indicated:
```
basic_string& erase(size_type pos = 0, size_type n = npos);
```
~~-1- Requires: pos <= size()~~
-2- Throws: out_of_range if pos > size().
[…]
Modify 27.4.3.7.6 [string.replace] as indicated: [Editorial note: The first change suggestion is also a bug fix of the current wording, because it is possible that this function can throw length_error, see p10]
```
basic_string&
  replace(size_type pos1, size_type n1,
          const basic_string& str);
```
~~-1- Requires: pos1 <= size().~~
~~-2- Throws: out_of_range if pos1 > size().~~
-3- Effects: ~~Calls~~Equivalent to return replace(pos1, n1, str.data(), str.size());.
~~-4- Returns: *this.~~
```
basic_string&
  replace(size_type pos1, size_type n1,
          const basic_string& str,
          size_type pos2, size_type n = npos);
```
~~-5- Requires: pos1 <= size() and pos2 <= str.size().~~
-6- Throws: out_of_range if pos1 > size() or pos2 > str.size().
[…]
```
basic_string&
  replace(size_type pos1, size_type n1, const charT* s, size_type n2);
```
-9- Requires: ~~pos1 <= size() and~~ s points to an array of at least n2 elements of charT.
-10- Throws: out_of_range if pos1 > size() or length_error if the length of the resulting string would exceed max_size() (see below).
[…]
```
basic_string&
  replace(size_type pos, size_type n, const charT* s);
```
-13- Requires: ~~pos <= size() and~~ s points to an array of at least traits::length(s) + 1 elements of charT.
-14- Effects: Equivalent to return replace(pos, n, s, traits::length(s));.
~~-15- Returns: *this.~~
Modify 27.4.3.7.7 [string.copy] as indicated:
```
size_type copy(charT* s, size_type n, size_type pos = 0) const;
```
~~-1- Requires: pos <= size()~~
-2- Throws: out_of_range if pos > size().
[…]
Modify 27.4.3.8.3 [string.substr] as indicated:
```
basic_string substr(size_type pos = 0, size_type n = npos) const;
```
~~-1- Requires: pos <= size()~~
-2- Throws: out_of_range if pos > size().
[…]
Modify 32.4.3.6 [thread.thread.member] as indicated:
```
void join();
```
~~-3- Requires: joinable() is true.~~
[…]
-7- Throws: system_error when an exception is required (30.2.2).
-8- Error conditions:
- […]
- invalid_argument — if the thread is not joinable.
```
void detach();
```
~~-9- Requires: joinable() is true.~~
[…]
-12- Throws: system_error when an exception is required (30.2.2).
-13- Error conditions:
- […]
- invalid_argument — if the thread is not joinable.