From 3c64582372cf445eabc4f9e99def7e33fb0270ee Mon Sep 17 00:00:00 2001 From: Jonathan Wakely Date: Tue, 31 Aug 2021 09:46:41 +0100 Subject: [PATCH] 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 gcc/ChangeLog: PR c++/60318 * doc/trouble.texi (Copy Assignment): Fix description of behaviour and fix code in example. --- 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 40c51ae21cb..8b34be4aa63 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