lib-symbol-visibility: Fix a misnomer

[Bruno Haible]

The macro DLL_EXPORTED was used for Windows-specific purposes in the beginning.
But since it possibly expands to
  __attribute__((__visibility__("default")))
on ELF, macOS, AIX, Cygwin platforms, it is no longer Windows-specific. But
the term "DLL" makes us think that it is. This patch fixes the misnomer.


2023-09-16  Bruno Haible  <bruno@clisp.org>

        lib-symbol-visibility: Fix a misnomer.
        * doc/lib-symbol-visibility.texi: Rename LIBFOO_DLL_EXPORTED to
        LIBFOO_SHLIB_EXPORTED. Prefer the term "shared library", since the term
        "DLL" applies only to Windows.
        * lib/relocatable.h (RELOCATABLE_SHLIB_EXPORTED): Renamed from
        RELOCATABLE_DLL_EXPORTED. Prefer the term "shared library", since the
        term "DLL" applies only to Windows.
        * lib/mbtowc-lock.c (SHLIB_EXPORTED): Renamed from DLL_EXPORTED.
        * lib/nl_langinfo-lock.c (SHLIB_EXPORTED): Likewise.
        * lib/setlocale-lock.c (SHLIB_EXPORTED): Likewise.

diff --git a/doc/lib-symbol-visibility.texi b/doc/lib-symbol-visibility.texi
index 5a3b3cdbfb..904c1fdc5d 100644
--- a/doc/lib-symbol-visibility.texi
+++ b/doc/lib-symbol-visibility.texi
@@ -140,16 +140,16 @@
 Define a macro specific to your library like this.
 @smallexample
 #if HAVE_VISIBILITY && BUILDING_LIBFOO
-# define LIBFOO_DLL_EXPORTED __attribute__((__visibility__("default")))
+# define LIBFOO_SHLIB_EXPORTED __attribute__((__visibility__("default")))
 #else
-# define LIBFOO_DLL_EXPORTED
+# define LIBFOO_SHLIB_EXPORTED
 #endif
 @end smallexample
 This macro should be enabled in all public header files of your library.
 
 @item
 Annotate all variable, function and class declarations in all public header
-files of your library with @samp{LIBFOO_DLL_EXPORTED}.  This annotation
+files of your library with @samp{LIBFOO_SHLIB_EXPORTED}.  This annotation
 can occur at different locations: between the @samp{extern} and the
 type or return type, or just before the entity being declared, or after
 the entire declarator.  My preference is to put it right after @samp{extern},
@@ -168,17 +168,17 @@
 the definition of the macro mentioned above, to something like this:
 @smallexample
 #if HAVE_VISIBILITY && BUILDING_LIBFOO
-# define LIBFOO_DLL_EXPORTED __attribute__((__visibility__("default")))
+# define LIBFOO_SHLIB_EXPORTED __attribute__((__visibility__("default")))
 #elif (defined _WIN32 && !defined __CYGWIN__) && @@BUILDING_SHARED@@ && 
BUILDING_LIBFOO
 # if defined DLL_EXPORT
-#  define LIBFOO_DLL_EXPORTED __declspec(dllexport)
+#  define LIBFOO_SHLIB_EXPORTED __declspec(dllexport)
 # else
-#  define LIBFOO_DLL_EXPORTED
+#  define LIBFOO_SHLIB_EXPORTED
 # endif
 #elif (defined _WIN32 && !defined __CYGWIN__) && @@BUILDING_SHARED@@
-# define LIBFOO_DLL_EXPORTED __declspec(dllimport)
+# define LIBFOO_SHLIB_EXPORTED __declspec(dllimport)
 #else
-# define LIBFOO_DLL_EXPORTED
+# define LIBFOO_SHLIB_EXPORTED
 #endif
 @end smallexample
 @noindent
@@ -198,5 +198,6 @@
 
 @noindent
 And @code{DLL_EXPORT} is defined by Libtool, on Windows platforms, when
-compiling for a DLL.  It is not defined when Libtool compiles an object
-file meant to be linked statically into some executable.
+compiling for a shared library (called DLL under Windows).
+It is not defined when Libtool compiles an object file meant to be linked
+statically into some executable.
diff --git a/lib/mbtowc-lock.c b/lib/mbtowc-lock.c
index 6ca6e10f94..c4d0b088f6 100644
--- a/lib/mbtowc-lock.c
+++ b/lib/mbtowc-lock.c
@@ -37,14 +37,14 @@ typedef int dummy;
 
 /* Macro for exporting a symbol (function, not variable) defined in this file,
    when compiled into a shared library.  */
-# ifndef DLL_EXPORTED
+# ifndef SHLIB_EXPORTED
 #  if HAVE_VISIBILITY
   /* Override the effect of the compiler option '-fvisibility=hidden'.  */
-#   define DLL_EXPORTED __attribute__((__visibility__("default")))
+#   define SHLIB_EXPORTED __attribute__((__visibility__("default")))
 #  elif defined _WIN32 || defined __CYGWIN__
-#   define DLL_EXPORTED __declspec(dllexport)
+#   define SHLIB_EXPORTED __declspec(dllexport)
 #  else
-#   define DLL_EXPORTED
+#   define SHLIB_EXPORTED
 #  endif
 # endif
 
@@ -59,7 +59,7 @@ typedef int dummy;
    because the latter is not guaranteed to be a stable ABI in the future.  */
 
 /* Make sure the function gets exported from DLLs.  */
-DLL_EXPORTED CRITICAL_SECTION *gl_get_mbtowc_lock (void);
+SHLIB_EXPORTED CRITICAL_SECTION *gl_get_mbtowc_lock (void);
 
 static glwthread_initguard_t guard = GLWTHREAD_INITGUARD_INIT;
 static CRITICAL_SECTION lock;
@@ -96,7 +96,7 @@ gl_get_mbtowc_lock (void)
 static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
 
 /* Make sure the function gets exported from shared libraries.  */
-DLL_EXPORTED pthread_mutex_t *gl_get_mbtowc_lock (void);
+SHLIB_EXPORTED pthread_mutex_t *gl_get_mbtowc_lock (void);
 
 /* Returns the internal lock used by mbrtowc and mbrtoc32.  */
 pthread_mutex_t *
@@ -123,7 +123,7 @@ atomic_init (void)
 }
 
 /* Make sure the function gets exported from shared libraries.  */
-DLL_EXPORTED mtx_t *gl_get_mbtowc_lock (void);
+SHLIB_EXPORTED mtx_t *gl_get_mbtowc_lock (void);
 
 /* Returns the internal lock used by mbrtowc and mbrtoc32.  */
 mtx_t *
diff --git a/lib/nl_langinfo-lock.c b/lib/nl_langinfo-lock.c
index e5cdcd3e77..fb12299959 100644
--- a/lib/nl_langinfo-lock.c
+++ b/lib/nl_langinfo-lock.c
@@ -37,14 +37,14 @@ typedef int dummy;
 
 /* Macro for exporting a symbol (function, not variable) defined in this file,
    when compiled into a shared library.  */
-# ifndef DLL_EXPORTED
+# ifndef SHLIB_EXPORTED
 #  if HAVE_VISIBILITY
   /* Override the effect of the compiler option '-fvisibility=hidden'.  */
-#   define DLL_EXPORTED __attribute__((__visibility__("default")))
+#   define SHLIB_EXPORTED __attribute__((__visibility__("default")))
 #  elif defined _WIN32 || defined __CYGWIN__
-#   define DLL_EXPORTED __declspec(dllexport)
+#   define SHLIB_EXPORTED __declspec(dllexport)
 #  else
-#   define DLL_EXPORTED
+#   define SHLIB_EXPORTED
 #  endif
 # endif
 
@@ -59,7 +59,7 @@ typedef int dummy;
    because the latter is not guaranteed to be a stable ABI in the future.  */
 
 /* Make sure the function gets exported from DLLs.  */
-DLL_EXPORTED CRITICAL_SECTION *gl_get_nl_langinfo_lock (void);
+SHLIB_EXPORTED CRITICAL_SECTION *gl_get_nl_langinfo_lock (void);
 
 static glwthread_initguard_t guard = GLWTHREAD_INITGUARD_INIT;
 static CRITICAL_SECTION lock;
@@ -96,7 +96,7 @@ gl_get_nl_langinfo_lock (void)
 static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
 
 /* Make sure the function gets exported from shared libraries.  */
-DLL_EXPORTED pthread_mutex_t *gl_get_nl_langinfo_lock (void);
+SHLIB_EXPORTED pthread_mutex_t *gl_get_nl_langinfo_lock (void);
 
 /* Returns the internal lock used by nl_langinfo.  */
 pthread_mutex_t *
@@ -123,7 +123,7 @@ atomic_init (void)
 }
 
 /* Make sure the function gets exported from shared libraries.  */
-DLL_EXPORTED mtx_t *gl_get_nl_langinfo_lock (void);
+SHLIB_EXPORTED mtx_t *gl_get_nl_langinfo_lock (void);
 
 /* Returns the internal lock used by nl_langinfo.  */
 mtx_t *
diff --git a/lib/relocatable.h b/lib/relocatable.h
index fcbbb21934..ae2a880c07 100644
--- a/lib/relocatable.h
+++ b/lib/relocatable.h
@@ -33,11 +33,11 @@ extern "C" {
 /* This can be enabled through the configure --enable-relocatable option.  */
 #if ENABLE_RELOCATABLE
 
-/* When building a DLL, we must export some functions.  Note that because
-   this is a private .h file, we don't need to use __declspec(dllimport)
-   in any case.  */
+/* When building a shared library, we must export some functions.
+   Note that because this is a private .h file, we don't need to use
+   __declspec(dllimport) in any case.  */
 #if HAVE_VISIBILITY && BUILDING_DLL
-# define RELOCATABLE_DLL_EXPORTED __attribute__((__visibility__("default")))
+# define RELOCATABLE_SHLIB_EXPORTED __attribute__((__visibility__("default")))
 #elif defined _MSC_VER && BUILDING_DLL
 /* When building with MSVC, exporting a symbol means that the object file
    contains a "linker directive" of the form /EXPORT:symbol.  This can be
@@ -45,16 +45,16 @@ extern "C" {
    "dumpbin /directives FILE" commands.
    The symbols from this file should be exported if and only if the object
    file gets included in a DLL.  Libtool, on Windows platforms, defines
-   the C macro DLL_EXPORT (together with PIC) when compiling for a DLL
-   and does not define it when compiling an object file meant to be linked
-   statically into some executable.  */
+   the C macro DLL_EXPORT (together with PIC) when compiling for a shared
+   library (called DLL under Windows) and does not define it when compiling
+   an object file meant to be linked statically into some executable.  */
 # if defined DLL_EXPORT
-#  define RELOCATABLE_DLL_EXPORTED __declspec(dllexport)
+#  define RELOCATABLE_SHLIB_EXPORTED __declspec(dllexport)
 # else
-#  define RELOCATABLE_DLL_EXPORTED
+#  define RELOCATABLE_SHLIB_EXPORTED
 # endif
 #else
-# define RELOCATABLE_DLL_EXPORTED
+# define RELOCATABLE_SHLIB_EXPORTED
 #endif
 
 /* Sets the original and the current installation prefix of the package.
@@ -62,7 +62,7 @@ extern "C" {
    by the corresponding pathname with the current prefix instead.  Both
    prefixes should be directory names without trailing slash (i.e. use ""
    instead of "/").  */
-extern RELOCATABLE_DLL_EXPORTED void
+extern RELOCATABLE_SHLIB_EXPORTED void
        set_relocation_prefix (const char *orig_prefix,
                               const char *curr_prefix);
 
diff --git a/lib/setlocale-lock.c b/lib/setlocale-lock.c
index b70ba09b00..593f63711b 100644
--- a/lib/setlocale-lock.c
+++ b/lib/setlocale-lock.c
@@ -37,14 +37,14 @@ typedef int dummy;
 
 /* Macro for exporting a symbol (function, not variable) defined in this file,
    when compiled into a shared library.  */
-# ifndef DLL_EXPORTED
+# ifndef SHLIB_EXPORTED
 #  if HAVE_VISIBILITY
   /* Override the effect of the compiler option '-fvisibility=hidden'.  */
-#   define DLL_EXPORTED __attribute__((__visibility__("default")))
+#   define SHLIB_EXPORTED __attribute__((__visibility__("default")))
 #  elif defined _WIN32 || defined __CYGWIN__
-#   define DLL_EXPORTED __declspec(dllexport)
+#   define SHLIB_EXPORTED __declspec(dllexport)
 #  else
-#   define DLL_EXPORTED
+#   define SHLIB_EXPORTED
 #  endif
 # endif
 
@@ -59,7 +59,7 @@ typedef int dummy;
    because the latter is not guaranteed to be a stable ABI in the future.  */
 
 /* Make sure the function gets exported from DLLs.  */
-DLL_EXPORTED CRITICAL_SECTION *gl_get_setlocale_null_lock (void);
+SHLIB_EXPORTED CRITICAL_SECTION *gl_get_setlocale_null_lock (void);
 
 static glwthread_initguard_t guard = GLWTHREAD_INITGUARD_INIT;
 static CRITICAL_SECTION lock;
@@ -96,7 +96,7 @@ gl_get_setlocale_null_lock (void)
 static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
 
 /* Make sure the function gets exported from shared libraries.  */
-DLL_EXPORTED pthread_mutex_t *gl_get_setlocale_null_lock (void);
+SHLIB_EXPORTED pthread_mutex_t *gl_get_setlocale_null_lock (void);
 
 /* Returns the internal lock used by setlocale_null_r.  */
 pthread_mutex_t *
@@ -123,7 +123,7 @@ atomic_init (void)
 }
 
 /* Make sure the function gets exported from shared libraries.  */
-DLL_EXPORTED mtx_t *gl_get_setlocale_null_lock (void);
+SHLIB_EXPORTED mtx_t *gl_get_setlocale_null_lock (void);
 
 /* Returns the internal lock used by setlocale_null_r.  */
 mtx_t *