Remove the vestigial support for custom API calling conventions

The computer industry has spoken rather clearly: we shall have
8-bit bytes, powers-of-2- and multiples-of-8-bit ints and floats,
one-size-fits-all pointers, and C API calling conventions for
system-level interoperability between applications and libraries.

So we're going to have all that and we're going to like it. Which
we do. We use the opportunity to shed annotations and make libpng
less baroque, both in interface and in implementation.

contrib/libtests/makepng.c

@@ -745,7 +745,7 @@ generate_row(png_bytep row, size_t rowbytes, unsigned int y, int color_type,
 }
 
 
-static void PNGCBAPI
+static void
 makepng_warning(png_structp png_ptr, png_const_charp message)
 {
    const char **ep = png_get_error_ptr(png_ptr);
@@ -760,7 +760,7 @@ makepng_warning(png_structp png_ptr, png_const_charp message)
   fprintf(stderr, "%s: warning: %s\n", name, message);
 }
 
-static void PNGCBAPI
+static void
 makepng_error(png_structp png_ptr, png_const_charp message)
 {
    makepng_warning(png_ptr, message);

contrib/libtests/pngimage.c

@@ -768,13 +768,13 @@ display_log(struct display *dp, error_level level, const char *fmt, ...)
 }
 
 /* error handler callbacks for libpng */
-static void PNGCBAPI
+static void
 display_warning(png_structp pp, png_const_charp warning)
 {
    display_log(get_dp(pp), LIBPNG_WARNING, "%s", warning);
 }
 
-static void PNGCBAPI
+static void
 display_error(png_structp pp, png_const_charp error)
 {
    struct display *dp = get_dp(pp);
@@ -858,7 +858,7 @@ buffer_read(struct display *dp, struct buffer *bp, png_bytep data,
    bp->read_count = read_count;
 }
 
-static void PNGCBAPI
+static void
 read_function(png_structp pp, png_bytep data, size_t size)
 {
    buffer_read(get_dp(pp), get_buffer(pp), data, size);
@@ -1325,7 +1325,7 @@ buffer_write(struct display *dp, struct buffer *buffer, png_bytep data,
    buffer->end_count = end_count;
 }
 
-static void PNGCBAPI
+static void
 write_function(png_structp pp, png_bytep data, size_t size)
 {
    buffer_write(get_dp(pp), get_buffer(pp), data, size);

contrib/libtests/pngunknown.c

@@ -457,7 +457,8 @@ clean_display(display *d)
    }
 }
 
-PNG_FUNCTION(void, display_exit, (display *d), static PNG_NORETURN)
+static PNG_NORETURN void
+display_exit(display *d)
 {
    ++(d->error_count);
 
@@ -480,16 +481,16 @@ display_rc(const display *d, int strict)
 }
 
 /* libpng error and warning callbacks */
-PNG_FUNCTION(void, (PNGCBAPI error), (png_structp png_ptr, const char *message),
-   static PNG_NORETURN)
+static PNG_NORETURN void
+error(png_structp png_ptr, const char *message)
 {
    display *d = (display*)png_get_error_ptr(png_ptr);
 
    fprintf(stderr, "%s(%s): libpng error: %s\n", d->file, d->test, message);
    display_exit(d);
 }
 
-static void PNGCBAPI
+static void
 warning(png_structp png_ptr, const char *message)
 {
    display *d = (display*)png_get_error_ptr(png_ptr);
@@ -531,7 +532,7 @@ get_valid(display *d, png_infop info_ptr)
 }
 
 #ifdef PNG_READ_USER_CHUNKS_SUPPORTED
-static int PNGCBAPI
+static int
 read_callback(png_structp pp, png_unknown_chunkp pc)
 {
    /* This function mimics the behavior of png_set_keep_unknown_chunks by

contrib/libtests/pngvalid.c

@@ -1093,7 +1093,7 @@ internal_error(png_store *ps, png_const_charp message)
 #endif /* PNG_READ_SUPPORTED */
 
 /* Functions to use as PNG callbacks. */
-static void PNGCBAPI
+static void
 store_error(png_structp ppIn, png_const_charp message) /* PNG_NORETURN */
 {
    png_const_structp pp = ppIn;
@@ -1109,7 +1109,7 @@ store_error(png_structp ppIn, png_const_charp message) /* PNG_NORETURN */
    }
 }
 
-static void PNGCBAPI
+static void
 store_warning(png_structp ppIn, png_const_charp message)
 {
    png_const_structp pp = ppIn;
@@ -1281,7 +1281,7 @@ valid_chunktype(png_uint_32 chunktype)
    return 1; /* It's valid */
 }
 
-static void PNGCBAPI
+static void
 store_write(png_structp ppIn, png_bytep pb, size_t st)
 {
    png_const_structp pp = ppIn;
@@ -1375,7 +1375,7 @@ store_write(png_structp ppIn, png_bytep pb, size_t st)
    ps->chunklen = chunklen;
 }
 
-static void PNGCBAPI
+static void
 store_flush(png_structp ppIn)
 {
    UNUSED(ppIn) /*DOES NOTHING*/
@@ -1700,7 +1700,7 @@ store_read_chunk(png_store *ps, png_bytep pb, size_t max, size_t min)
    return st; /* space left */
 }
 
-static void PNGCBAPI
+static void
 store_read(png_structp ppIn, png_bytep pb, size_t st)
 {
    png_const_structp pp = ppIn;
@@ -1903,7 +1903,7 @@ store_pool_delete(png_store *ps, store_pool *pool)
 }
 
 /* The memory callbacks: */
-static png_voidp PNGCBAPI
+static png_voidp
 store_malloc(png_structp ppIn, png_alloc_size_t cb)
 {
    png_const_structp pp = ppIn;
@@ -1952,7 +1952,7 @@ store_malloc(png_structp ppIn, png_alloc_size_t cb)
    return new;
 }
 
-static void PNGCBAPI
+static void
 store_free(png_structp ppIn, png_voidp memory)
 {
    png_const_structp pp = ppIn;
@@ -3198,7 +3198,7 @@ modifier_read_imp(png_modifier *pm, png_bytep pb, size_t st)
 }
 
 /* The callback: */
-static void PNGCBAPI
+static void
 modifier_read(png_structp ppIn, png_bytep pb, size_t st)
 {
    png_const_structp pp = ppIn;
@@ -5391,7 +5391,7 @@ standard_info_imp(standard_display *dp, png_structp pp, png_infop pi,
    standard_info_part2(dp, pp, pi, nImages);
 }
 
-static void PNGCBAPI
+static void
 standard_info(png_structp pp, png_infop pi)
 {
    standard_display *dp = voidcast(standard_display*,
@@ -5403,7 +5403,7 @@ standard_info(png_structp pp, png_infop pi)
    standard_info_imp(dp, pp, pi, 1 /*only one image*/);
 }
 
-static void PNGCBAPI
+static void
 progressive_row(png_structp ppIn, png_bytep new_row, png_uint_32 y, int pass)
 {
    png_const_structp pp = ppIn;
@@ -5703,7 +5703,7 @@ standard_image_validate(standard_display *dp, png_const_structp pp, int iImage,
    dp->ps->validated = 1;
 }
 
-static void PNGCBAPI
+static void
 standard_end(png_structp ppIn, png_infop pi)
 {
    png_const_structp pp = ppIn;
@@ -6703,7 +6703,7 @@ transform_info_imp(transform_display *dp, png_structp pp, png_infop pi)
    }
 }
 
-static void PNGCBAPI
+static void
 transform_info(png_structp pp, png_infop pi)
 {
    transform_info_imp(voidcast(transform_display*, png_get_progressive_ptr(pp)),
@@ -6919,7 +6919,7 @@ transform_image_validate(transform_display *dp, png_const_structp pp,
    dp->this.ps->validated = 1;
 }
 
-static void PNGCBAPI
+static void
 transform_end(png_structp ppIn, png_infop pi)
 {
    png_const_structp pp = ppIn;
@@ -9385,7 +9385,7 @@ gamma_info_imp(gamma_display *dp, png_structp pp, png_infop pi)
    standard_info_part2(&dp->this, pp, pi, 1 /*images*/);
 }
 
-static void PNGCBAPI
+static void
 gamma_info(png_structp pp, png_infop pi)
 {
    gamma_info_imp(voidcast(gamma_display*, png_get_progressive_ptr(pp)), pp,
@@ -10385,7 +10385,7 @@ gamma_image_validate(gamma_display *dp, png_const_structp pp,
    dp->this.ps->validated = 1;
 }
 
-static void PNGCBAPI
+static void
 gamma_end(png_structp ppIn, png_infop pi)
 {
    png_const_structp pp = ppIn;

contrib/tools/pngcp.c

@@ -1674,7 +1674,7 @@ makename(struct display *dp, const char *dir, const char *infile)
 }
 
 /* error handler callbacks for libpng */
-static void PNGCBAPI
+static void
 display_warning(png_structp pp, png_const_charp warning)
 {
    struct display *dp = get_dp(pp);
@@ -1684,7 +1684,7 @@ display_warning(png_structp pp, png_const_charp warning)
       display_log(get_dp(pp), LIBPNG_WARNING, "%s", warning);
 }
 
-static void PNGCBAPI
+static void
 display_error(png_structp pp, png_const_charp error)
 {
    struct display *dp = get_dp(pp);
@@ -1716,7 +1716,7 @@ display_start_read(struct display *dp, const char *filename)
       display_log(dp, USER_ERROR, "file open failed (%s)", strerror(errno));
 }
 
-static void PNGCBAPI
+static void
 read_function(png_structp pp, png_bytep data, size_t size)
 {
    struct display *dp = get_dp(pp);
@@ -1896,7 +1896,7 @@ display_start_write(struct display *dp, const char *filename)
    }
 }
 
-static void PNGCBAPI
+static void
 write_function(png_structp pp, png_bytep data, size_t size)
 {
    struct display *dp = get_dp(pp);

contrib/tools/pngfix.c

@@ -3149,13 +3149,13 @@ read_chunk(struct file *file)
 /* This returns a file* from a png_struct in an implementation specific way. */
 static struct file *get_control(png_const_structrp png_ptr);
 
-static void PNGCBAPI
+static void
 error_handler(png_structp png_ptr, png_const_charp message)
 {
    stop(get_control(png_ptr),  LIBPNG_ERROR_CODE, message);
 }
 
-static void PNGCBAPI
+static void
 warning_handler(png_structp png_ptr, png_const_charp message)
 {
    struct file *file = get_control(png_ptr);
@@ -3167,7 +3167,7 @@ warning_handler(png_structp png_ptr, png_const_charp message)
 /* Read callback - this is where the work gets done to check the stream before
  * passing it to libpng
  */
-static void PNGCBAPI
+static void
 read_callback(png_structp png_ptr, png_bytep buffer, size_t count)
    /* Return 'count' bytes to libpng in 'buffer' */
 {

manuals/libpng-install.txt

@@ -345,30 +345,11 @@ way pngusr.h is used in the build has been changed; however, library
 builders will probably want to examine the changes to take advantage of
 new capabilities and to simplify their build system.
 
-A. Specific changes to library configuration capabilities
-
-The exact mechanism used to control attributes of API functions has
-changed.  A single set of operating system independent macro definitions
-is used and operating system specific directives are defined in
-pnglibconf.h
-
-As part of this the mechanism used to choose procedure call standards on
-those systems that allow a choice has been changed.  At present this only
-affects certain Microsoft (DOS, Windows) and IBM (OS/2) operating systems
-running on Intel processors.  As before, PNGAPI is defined where required
-to control the exported API functions; however, two new macros, PNGCBAPI
-and PNGCAPI, are used instead for callback functions (PNGCBAPI) and
-(PNGCAPI) for functions that must match a C library prototype (currently
-only png_longjmp_ptr, which must match the C longjmp function.)  The new
-approach is documented in pngconf.h
-
-Despite these changes, libpng 1.5.0 only supports the native C function
-calling standard on those platforms tested so far ("__cdecl" on Microsoft
-Windows).  This is because the support requirements for alternative
-calling conventions seem to no longer exist.  Developers who find it
-necessary to set PNG_API_RULE to 1 should advise the mailing list
-(png-mng-implement) of this and library builders who use Openwatcom and
-therefore set PNG_API_RULE to 2 should also contact the mailing list.
+A. Changes to the library configuration capabilities
+
+A new mechanism to control attributes of API functions was introduced in
+libpng-1.5.0.  A single set of system-independent macro definitions and
+directives is defined in pnglibconf.h
 
 B. Changes to the configuration mechanism
 

manuals/libpng-manual.txt

@@ -5317,13 +5317,13 @@ We don't use C++ style ("//") comments. We have, however,
 used them in the past in some now-abandoned MMX assembler
 code.
 
-Functions and their curly braces are not indented, and
-exported functions are marked with PNGAPI:
+Functions and their curly braces are not indented. We used to mark
+the exported functions with PNGAPI, but we no longer do:
 
  /* This is a public function that is visible to
   * application programmers. It does thus-and-so.
   */
- void PNGAPI
+ void
  png_exported_function(png_ptr, png_info, foo)
  {
     body;

manuals/libpng.3

@@ -5826,13 +5826,13 @@ We don't use C++ style ("//") comments. We have, however,
 used them in the past in some now-abandoned MMX assembler
 code.
 
-Functions and their curly braces are not indented, and
-exported functions are marked with PNGAPI:
+Functions and their curly braces are not indented. We used to mark
+the exported functions with PNGAPI, but we no longer do:
 
  /* This is a public function that is visible to
   * application programmers. It does thus-and-so.
   */
- void PNGAPI
+ void
  png_exported_function(png_ptr, png_info, foo)
  {
     body;