search: Fix compilation errors with SunPRO C++ on Solaris 10

[Bruno Haible]

On Solaris 10, with cc and CC as compilers, I get these compilation errors:

"../gllib/search.h", line 565: Error: Cannot return extern "C" void*(*)(const 
void*,const void*,unsigned*,unsigned,extern "C" int(*)(const void*,const 
void*)) from a function that should return void*(*)(const void*,const 
void*,unsigned*,unsigned,int(*)(const void*,const void*)).
"../gllib/search.h", line 587: Error: Cannot return extern "C" void*(*)(const 
void*,void*,unsigned*,unsigned,extern "C" int(*)(const void*,const void*)) from 
a function that should return void*(*)(const 
void*,void*,unsigned*,unsigned,int(*)(const void*,const void*)).

Apparently this compiler is picky regarding C linkage vs. C++ linkage of
function types. This patch fixes it.


2021-12-24  Bruno Haible  <bruno@clisp.org>

        search: Fix compilation errors with SunPRO C++ on Solaris 10.
        * lib/search.in.h (_gl_lsearch_compar_fn): New type.
        (lfind, lsearch): Use it.

diff --git a/lib/search.in.h b/lib/search.in.h
index 02faf482d..1935d8a97 100644
--- a/lib/search.in.h
+++ b/lib/search.in.h
@@ -38,6 +38,17 @@
 /* The definition of _GL_WARN_ON_USE is copied here.  */
 
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+#if !GNULIB_defined_lsearch_fn_types
+typedef int (*_gl_lsearch_compar_fn) (const void *, const void *);
+# define GNULIB_defined_lsearch_fn_types 1
+#endif
+#ifdef __cplusplus
+}
+#endif
+
 #if @GNULIB_MDA_LFIND@
 /* On native Windows, map 'lfind' to '_lfind', so that -loldnames is not
    required.  In C++ with GNULIB_NAMESPACE, avoid differences between
@@ -50,12 +61,12 @@
 _GL_CXXALIAS_MDA (lfind, void *,
                   (const void *key, const void *base, unsigned int *nmemb,
                    unsigned int size,
-                   int (*compar) (const void *, const void *)));
+                   _gl_lsearch_compar_fn compar));
 # else
 _GL_CXXALIAS_SYS (lfind, void *,
                   (const void *key, const void *base, size_t *nmemb,
                    size_t size,
-                   int (*compar) (const void *, const void *)));
+                   _gl_lsearch_compar_fn compar));
 # endif
 _GL_CXXALIASWARN (lfind);
 #endif
@@ -72,12 +83,12 @@ _GL_CXXALIASWARN (lfind);
 _GL_CXXALIAS_MDA (lsearch, void *,
                   (const void *key, void *base, unsigned int *nmemb,
                    unsigned int size,
-                   int (*compar) (const void *, const void *)));
+                   _gl_lsearch_compar_fn compar));
 # else
 _GL_CXXALIAS_SYS (lsearch, void *,
                   (const void *key, void *base, size_t *nmemb,
                    size_t size,
-                   int (*compar) (const void *, const void *)));
+                   _gl_lsearch_compar_fn compar));
 # endif
 _GL_CXXALIASWARN (lsearch);
 #endif