From: Jan Rheinländer <jrheinlaender@gmx.de>
Date: Wed, 16 Feb 2022 22:57:36 +0000 (+0100)
Subject: Work around a compiler bug on MSVC.
X-Git-Tag: release_1-8-3~2
X-Git-Url: https://www.ginac.de/ginac.git//ginac.git?a=commitdiff_plain;h=b98ef824450d2897f5ea8f5254d614e6f8148d33;p=ginac.git

Work around a compiler bug on MSVC.

The two 'reg_info' declarations introduced in f271f67d2f turned out
to confuse MSVC: It thinks that these declarations are definitions
and then complains about a missing default ctor (error C2512) and
about duplicate definitions later in the .cpp files (error C2766).

But the standard says in [temp.expl.spec] §13:
An explicit specialization of a static data member of a template or
an explicit specialization of a static  data member template is a
definition if the declaration includes an initializer; otherwise, it
is a declaration. [Note: The definition of a static data member of a
template that requires default-initialization must use a braced-init-
list:
    template<> X Q<int>::x;     // declaration
    template<> X Q<int>::x ();  // error: declares a function
    template<> X Q<int>::x { }; // definition
--end note]
There is no initializer at lst.h:35 and at exprseq.h:35. Hence, this
is merely a declaration and the compiler's error message is wrong.
Let's work around by #ifndef'ing the two lines for silly MSVC.
---

diff --git a/ginac/exprseq.h b/ginac/exprseq.h
index dea1e38e..ce78aae9 100644
--- a/ginac/exprseq.h
+++ b/ginac/exprseq.h
@@ -32,7 +32,9 @@ namespace GiNaC {
 typedef container<std::vector> exprseq;
 
 /** Declaration of container::reg_info for exprseq. */
+#ifndef _MSC_VER  // workaround error C2766: explicit specialization; 'reg_info' has already been defined
 template<> registered_class_info exprseq::reg_info;
+#endif
 
 // defined in exprseq.cpp
 template<> bool exprseq::info(unsigned inf) const;
diff --git a/ginac/lst.h b/ginac/lst.h
index 6b047c69..1dae29ee 100644
--- a/ginac/lst.h
+++ b/ginac/lst.h
@@ -32,7 +32,9 @@ namespace GiNaC {
 typedef container<std::list> lst;
 
 /** Declaration of container::reg_info for lst. */
+#ifndef _MSC_VER  // workaround error C2766: explicit specialization; 'reg_info' has already been defined
 template<> registered_class_info lst::reg_info;
+#endif
 
 /** Specialization of container::get_default_flags() for lst. */
 template<> inline unsigned lst::get_default_flags() { return status_flags::not_shareable; }