https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65230
Bug ID: 65230
Summary: pretty-print inconsistent output for similar objects
Product: gcc
Version: 5.0
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: msebor at gcc dot gnu.org
The libstdc++ pretty printer produces inconsistent output for objects with
similar properties, making it more difficult than necessary to interpret. For
example, an "empty" bitset object (one consisting of no bits, or one with no
bits set) is printed simply as "std::bitset" while an empty std::tuple<> is
printed as "empty std::tuple". A std::vector<bool> of size 0 is printed to
include its size and capacity, while a non-empty vector<bool> also includes its
elements. An example is below.
I'd like to propose that the value of an empty object be printed as "{ }"
regardless of its type. I.e., a std::bitset<0> as "std::bitset { }", a
std::tuple<> as "std::tuple<> { }", and an empty std::vector<T> as
"std::vector<T> of length 0, capacity N = { }"
$ g++ -g -std=c++11 t.cpp && gdb -batch -ex "b foo" -ex "r" -ex "p b0" -ex "p
b1" -ex "p t0" -ex "p t1" -ex "p v0" -ex "p v1" -q a.out
Breakpoint 1 at 0x100008a8: file t.cpp, line 9.
Python Exception <class 'gdb.error'> There is no member or method named _M_w.:
Breakpoint 1, foo(std::bitset<0ul>, std::bitset<1ul>, std::tuple<>,
std::tuple<int>, std::vector<bool, std::allocator<bool> >, std::vector<bool,
std::allocator<bool> >) (b0=std::bitset, b1=std::bitset, t0=empty std::tuple,
t1=std::tuple containing = {...}, v0=std::vector<bool> of length 0, capacity 0,
v1=std::vector<bool> of length 1, capacity 64 = {...}) at t.cpp:9
9 }
Python Exception <class 'gdb.error'> There is no member or method named _M_w.:
$1 = std::bitset
$2 = std::bitset
$3 = empty std::tuple
$4 = std::tuple containing = {[1] = 0}
$5 = std::vector<bool> of length 0, capacity 0
$6 = std::vector<bool> of length 1, capacity 64 = {0}
