loaders: Change method used to not unload loaders

It appears that in certain environments (homebrew on MacOS) the linker
does not like the -z nodelete option, so handle this differently.

old/legacy-imlib2#8

src/lib/Imlib2_Loader.h

@@ -197,24 +197,33 @@ int                 __imlib_LoadProgressRows(ImlibImage * im,
 
 #define IMLIB2_LOADER_VERSION 2
 
+#define LDR_FLAG_KEEP   0x01    /* Don't unload loader */
+
 typedef struct {
    unsigned char       ldr_version;     /* Module ABI version */
-   unsigned char       rsvd;
+   unsigned char       ldr_flags;       /* LDR_FLAG_... */
    unsigned short      num_formats;     /* Length og known extension list */
    const char         *const *formats;  /* Known extension list */
    int                 (*load)(ImlibImage * im, int load_data);
    int                 (*save)(ImlibImage * im);
 } ImlibLoaderModule;
 
-#define IMLIB_LOADER(_fmts, _ldr, _svr) \
+#define IMLIB_LOADER_(_fmts, _ldr, _svr, _flags) \
     __EXPORT__ ImlibLoaderModule loader = { \
         .ldr_version = IMLIB2_LOADER_VERSION, \
+        .ldr_flags = _flags, \
         .num_formats = ARRAY_SIZE(_fmts), \
         .formats = _fmts, \
         .load = _ldr, \
         .save = _svr, \
     }
 
+#define IMLIB_LOADER(_fmts, _ldr, _svr) \
+    IMLIB_LOADER_(_fmts, _ldr, _svr, 0)
+
+#define IMLIB_LOADER_KEEP(_fmts, _ldr, _svr) \
+    IMLIB_LOADER_(_fmts, _ldr, _svr, LDR_FLAG_KEEP)
+
 #define QUIT_WITH_RC(_err) { rc = _err; goto quit; }
 
 #define PCAST(T, p) ((T)(const void *)(p))

src/lib/loaders.c

@@ -15,6 +15,7 @@
 #define DP(fmt...) DC(DBG_LOAD, fmt)
 
 static ImlibLoader *loaders = NULL;
+static ImlibLoader *loaders_unloaded = NULL;
 static char         loaders_loaded = 0;
 
 typedef struct {
@@ -161,11 +162,24 @@ __imlib_LookupLoaderByModulePath(const char *file)
 static ImlibLoader *
 __imlib_ProduceLoader(const char *file)
 {
-   ImlibLoader        *l;
+   ImlibLoader        *l, *l_prev;
    ImlibLoaderModule  *m;
 
    DP("%s: %s\n", __func__, file);
 
+   /* Check unloaded loaders */
+   for (l = loaders_unloaded, l_prev = NULL; l; l_prev = l, l = l->next)
+     {
+        if (strcmp(file, l->file) != 0)
+           continue;
+
+        if (l == loaders_unloaded)
+           loaders_unloaded = l->next;
+        else
+           l_prev->next = l->next;
+        goto found;
+     }
+
    l = malloc(sizeof(ImlibLoader));
 
    l->handle = dlopen(file, RTLD_NOW | RTLD_LOCAL);
@@ -187,6 +201,7 @@ __imlib_ProduceLoader(const char *file)
    l->file = strdup(file);
    l->name = m->formats[0];
 
+ found:
    l->next = loaders;
    loaders = l;
 
@@ -201,9 +216,18 @@ __imlib_ProduceLoader(const char *file)
 static void
 __imlib_ConsumeLoader(ImlibLoader * l)
 {
-   free(l->file);
+   if (l->module->ldr_flags & LDR_FLAG_KEEP)
+     {
+        /* Not un/re-loadable - Move to unloaded loaders list */
+        l->next = loaders_unloaded;
+        loaders_unloaded = l;
+        return;
+     }
+
    if (l->handle)
       dlclose(l->handle);
+
+   free(l->file);
    free(l);
 }
 

src/lib/loaders.h

@@ -5,9 +5,11 @@
 
 #define IMLIB2_LOADER_VERSION 2
 
+#define LDR_FLAG_KEEP   0x01    /* Don't unload loader */
+
 typedef struct {
    unsigned char       ldr_version;     /* Module ABI version */
-   unsigned char       rsvd;
+   unsigned char       ldr_flags;       /* LDR_FLAG_... */
    unsigned short      num_formats;     /* Length og known extension list */
    const char         *const *formats;  /* Known extension list */
    int                 (*load)(ImlibImage * im, int load_data);

src/modules/loaders/Makefile.am

@@ -91,7 +91,7 @@ gif_la_LIBTOOLFLAGS  = --tag=disable-static
 
 heif_la_SOURCES      = loader_heif.c
 heif_la_CPPFLAGS     = $(HEIF_CFLAGS) $(AM_CPPFLAGS)
-heif_la_LDFLAGS      = -module -avoid-version -Wl,-z,nodelete
+heif_la_LDFLAGS      = -module -avoid-version
 heif_la_LIBADD       = $(HEIF_LIBS) $(top_builddir)/src/lib/libImlib2.la
 heif_la_LIBTOOLFLAGS = --tag=disable-static
 
@@ -142,7 +142,7 @@ ps_la_LIBTOOLFLAGS  = --tag=disable-static
 
 svg_la_SOURCES       = loader_svg.c
 svg_la_CPPFLAGS      = $(SVG_CFLAGS) $(AM_CPPFLAGS)
-svg_la_LDFLAGS       = -module -avoid-version -Wl,-z,nodelete
+svg_la_LDFLAGS       = -module -avoid-version
 svg_la_LIBADD        = $(SVG_LIBS) $(top_builddir)/src/lib/libImlib2.la
 svg_la_LIBTOOLFLAGS  = --tag=disable-static
 

src/modules/loaders/loader_heif.c

@@ -172,4 +172,4 @@ _load(ImlibImage * im, int load_data)
    return rc;
 }
 
-IMLIB_LOADER(_formats, _load, NULL);
+IMLIB_LOADER_KEEP(_formats, _load, NULL);

src/modules/loaders/loader_svg.c

@@ -238,4 +238,4 @@ _load(ImlibImage * im, int load_data)
    return rc;
 }
 
-IMLIB_LOADER(_formats, _load, NULL);
+IMLIB_LOADER_KEEP(_formats, _load, NULL);