[gcc r12-2052] X86: Provide a CTOR for stringop_algs [PR100246].

[gcc r12-2052] X86: Provide a CTOR for stringop_algs [PR100246].

[Iain D Sandoe]

https://gcc.gnu.org/g:f99f6eb58e1f894dae024f63cc2fe30fa7605e59

commit r12-2052-gf99f6eb58e1f894dae024f63cc2fe30fa7605e59
Author: Iain Sandoe <iain@sandoe.co.uk>
Date:   Sat Jul 3 19:47:48 2021 +0100

    X86: Provide a CTOR for stringop_algs [PR100246].
    
    Several older compilers fail to build modern GCC because of missing
    or incomplete C++11 support.
    
    Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>
    
    PR bootstrap/100246 - [11/12 Regression] GCC will not bootstrap with clang 3.4/3.5 [xcode 5/6, Darwin 12/13]
    
            PR bootstrap/100246
    
    gcc/ChangeLog:
    
            * config/i386/i386.h (struct stringop_algs): Define a CTOR for
            this type.

Diff:
---
 gcc/config/i386/i386.h | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/gcc/config/i386/i386.h b/gcc/config/i386/i386.h
index 6e0340a4b60..03d176143fe 100644
--- a/gcc/config/i386/i386.h
+++ b/gcc/config/i386/i386.h
@@ -73,6 +73,15 @@ struct stringop_algs
 {
   const enum stringop_alg unknown_size;
   const struct stringop_strategy {
+    /* Several older compilers delete the default constructor because of the
+       const entries (see PR100246).  Manually specifying a CTOR works around
+       this issue.  Since this header is used by code compiled with the C
+       compiler we must guard the addition.  */
+#ifdef __cplusplus
+    stringop_strategy(int _max = -1, enum stringop_alg _alg = libcall,
+		      int _noalign = false)
+      : max (_max), alg (_alg), noalign (_noalign) {}
+#endif
     const int max;
     const enum stringop_alg alg;
     int noalign;