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* [gcc r9-9715] c++: Fix docs on assignment of virtual bases [PR60318]
@ 2021-09-08 23:34 Jonathan Wakely
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From: Jonathan Wakely @ 2021-09-08 23:34 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:03b8e26897fbddec10a703cf518280af675e6458
commit r9-9715-g03b8e26897fbddec10a703cf518280af675e6458
Author: Jonathan Wakely <jwakely@redhat.com>
Date: Tue Aug 31 09:46:41 2021 +0100
c++: Fix docs on assignment of virtual bases [PR60318]
The description of behaviour is incorrect, the virtual base gets
assigned before entering the bodies of A::operator= and B::operator=,
not after.
The example is also ill-formed (passing a string literal to char*) and
undefined (missing return from Base::operator=).
Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
gcc/ChangeLog:
PR c++/60318
* doc/trouble.texi (Copy Assignment): Fix description of
behaviour and fix code in example.
(cherry picked from commit 3c64582372cf445eabc4f9e99def7e33fb0270ee)
Diff:
---
gcc/doc/trouble.texi | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/gcc/doc/trouble.texi b/gcc/doc/trouble.texi
index 693912ea355..aaee8fba6bb 100644
--- a/gcc/doc/trouble.texi
+++ b/gcc/doc/trouble.texi
@@ -865,10 +865,11 @@ objects behave unspecified when being assigned. For example:
@smallexample
struct Base@{
char *name;
- Base(char *n) : name(strdup(n))@{@}
+ Base(const char *n) : name(strdup(n))@{@}
Base& operator= (const Base& other)@{
free (name);
name = strdup (other.name);
+ return *this;
@}
@};
@@ -901,8 +902,8 @@ inside @samp{func} in the example).
G++ implements the ``intuitive'' algorithm for copy-assignment: assign all
direct bases, then assign all members. In that algorithm, the virtual
base subobject can be encountered more than once. In the example, copying
-proceeds in the following order: @samp{val}, @samp{name} (via
-@code{strdup}), @samp{bval}, and @samp{name} again.
+proceeds in the following order: @samp{name} (via @code{strdup}),
+@samp{val}, @samp{name} again, and @samp{bval}.
If application code relies on copy-assignment, a user-defined
copy-assignment operator removes any uncertainties. With such an
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