chore: Add, relocate or rephrase debug statements, for better clarity

pngget.c

@@ -1,7 +1,7 @@
 
 /* pngget.c - retrieval of values from info struct
  *
- * Copyright (c) 2018-2023 Cosmin Truta
+ * Copyright (c) 2018-2024 Cosmin Truta
  * Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson
  * Copyright (c) 1996-1997 Andreas Dilger
  * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
@@ -127,12 +127,11 @@ png_get_x_pixels_per_meter(png_const_structrp png_ptr, png_const_inforp
    info_ptr)
 {
 #ifdef PNG_pHYs_SUPPORTED
+   png_debug(1, "in png_get_x_pixels_per_meter");
+
    if (png_ptr != NULL && info_ptr != NULL &&
        (info_ptr->valid & PNG_INFO_pHYs) != 0)
    {
-         png_debug1(1, "in %s retrieval function",
-             "png_get_x_pixels_per_meter");
-
       if (info_ptr->phys_unit_type == PNG_RESOLUTION_METER)
          return (info_ptr->x_pixels_per_unit);
    }
@@ -149,12 +148,11 @@ png_get_y_pixels_per_meter(png_const_structrp png_ptr, png_const_inforp
     info_ptr)
 {
 #ifdef PNG_pHYs_SUPPORTED
+   png_debug(1, "in png_get_y_pixels_per_meter");
+
    if (png_ptr != NULL && info_ptr != NULL &&
        (info_ptr->valid & PNG_INFO_pHYs) != 0)
    {
-      png_debug1(1, "in %s retrieval function",
-          "png_get_y_pixels_per_meter");
-
       if (info_ptr->phys_unit_type == PNG_RESOLUTION_METER)
          return (info_ptr->y_pixels_per_unit);
    }
@@ -170,11 +168,11 @@ png_uint_32 PNGAPI
 png_get_pixels_per_meter(png_const_structrp png_ptr, png_const_inforp info_ptr)
 {
 #ifdef PNG_pHYs_SUPPORTED
+   png_debug(1, "in png_get_pixels_per_meter");
+
    if (png_ptr != NULL && info_ptr != NULL &&
        (info_ptr->valid & PNG_INFO_pHYs) != 0)
    {
-      png_debug1(1, "in %s retrieval function", "png_get_pixels_per_meter");
-
       if (info_ptr->phys_unit_type == PNG_RESOLUTION_METER &&
           info_ptr->x_pixels_per_unit == info_ptr->y_pixels_per_unit)
          return (info_ptr->x_pixels_per_unit);
@@ -193,11 +191,11 @@ png_get_pixel_aspect_ratio(png_const_structrp png_ptr, png_const_inforp
    info_ptr)
 {
 #ifdef PNG_READ_pHYs_SUPPORTED
+   png_debug(1, "in png_get_pixel_aspect_ratio");
+
    if (png_ptr != NULL && info_ptr != NULL &&
        (info_ptr->valid & PNG_INFO_pHYs) != 0)
    {
-      png_debug1(1, "in %s retrieval function", "png_get_aspect_ratio");
-
       if (info_ptr->x_pixels_per_unit != 0)
          return ((float)((float)info_ptr->y_pixels_per_unit
              /(float)info_ptr->x_pixels_per_unit));
@@ -217,6 +215,8 @@ png_get_pixel_aspect_ratio_fixed(png_const_structrp png_ptr,
     png_const_inforp info_ptr)
 {
 #ifdef PNG_READ_pHYs_SUPPORTED
+   png_debug(1, "in png_get_pixel_aspect_ratio_fixed");
+
    if (png_ptr != NULL && info_ptr != NULL &&
        (info_ptr->valid & PNG_INFO_pHYs) != 0 &&
        info_ptr->x_pixels_per_unit > 0 && info_ptr->y_pixels_per_unit > 0 &&
@@ -225,8 +225,6 @@ png_get_pixel_aspect_ratio_fixed(png_const_structrp png_ptr,
    {
       png_fixed_point res;
 
-      png_debug1(1, "in %s retrieval function", "png_get_aspect_ratio_fixed");
-
       /* The following casts work because a PNG 4 byte integer only has a valid
        * range of 0..2^31-1; otherwise the cast might overflow.
        */
@@ -247,11 +245,11 @@ png_int_32 PNGAPI
 png_get_x_offset_microns(png_const_structrp png_ptr, png_const_inforp info_ptr)
 {
 #ifdef PNG_oFFs_SUPPORTED
+   png_debug(1, "in png_get_x_offset_microns");
+
    if (png_ptr != NULL && info_ptr != NULL &&
        (info_ptr->valid & PNG_INFO_oFFs) != 0)
    {
-      png_debug1(1, "in %s retrieval function", "png_get_x_offset_microns");
-
       if (info_ptr->offset_unit_type == PNG_OFFSET_MICROMETER)
          return (info_ptr->x_offset);
    }
@@ -267,11 +265,11 @@ png_int_32 PNGAPI
 png_get_y_offset_microns(png_const_structrp png_ptr, png_const_inforp info_ptr)
 {
 #ifdef PNG_oFFs_SUPPORTED
+   png_debug(1, "in png_get_y_offset_microns");
+
    if (png_ptr != NULL && info_ptr != NULL &&
        (info_ptr->valid & PNG_INFO_oFFs) != 0)
    {
-      png_debug1(1, "in %s retrieval function", "png_get_y_offset_microns");
-
       if (info_ptr->offset_unit_type == PNG_OFFSET_MICROMETER)
          return (info_ptr->y_offset);
    }
@@ -287,11 +285,11 @@ png_int_32 PNGAPI
 png_get_x_offset_pixels(png_const_structrp png_ptr, png_const_inforp info_ptr)
 {
 #ifdef PNG_oFFs_SUPPORTED
+   png_debug(1, "in png_get_x_offset_pixels");
+
    if (png_ptr != NULL && info_ptr != NULL &&
        (info_ptr->valid & PNG_INFO_oFFs) != 0)
    {
-      png_debug1(1, "in %s retrieval function", "png_get_x_offset_pixels");
-
       if (info_ptr->offset_unit_type == PNG_OFFSET_PIXEL)
          return (info_ptr->x_offset);
    }
@@ -307,11 +305,11 @@ png_int_32 PNGAPI
 png_get_y_offset_pixels(png_const_structrp png_ptr, png_const_inforp info_ptr)
 {
 #ifdef PNG_oFFs_SUPPORTED
+   png_debug(1, "in png_get_y_offset_pixels");
+
    if (png_ptr != NULL && info_ptr != NULL &&
        (info_ptr->valid & PNG_INFO_oFFs) != 0)
    {
-      png_debug1(1, "in %s retrieval function", "png_get_y_offset_pixels");
-
       if (info_ptr->offset_unit_type == PNG_OFFSET_PIXEL)
          return (info_ptr->y_offset);
    }
@@ -434,11 +432,11 @@ png_get_pHYs_dpi(png_const_structrp png_ptr, png_const_inforp info_ptr,
 {
    png_uint_32 retval = 0;
 
+   png_debug1(1, "in %s retrieval function", "pHYs");
+
    if (png_ptr != NULL && info_ptr != NULL &&
        (info_ptr->valid & PNG_INFO_pHYs) != 0)
    {
-      png_debug1(1, "in %s retrieval function", "pHYs");
-
       if (res_x != NULL)
       {
          *res_x = info_ptr->x_pixels_per_unit;
@@ -499,12 +497,12 @@ png_uint_32 PNGAPI
 png_get_bKGD(png_const_structrp png_ptr, png_inforp info_ptr,
     png_color_16p *background)
 {
+   png_debug1(1, "in %s retrieval function", "bKGD");
+
    if (png_ptr != NULL && info_ptr != NULL &&
        (info_ptr->valid & PNG_INFO_bKGD) != 0 &&
        background != NULL)
    {
-      png_debug1(1, "in %s retrieval function", "bKGD");
-
       *background = &(info_ptr->background);
       return (PNG_INFO_bKGD);
    }
@@ -524,6 +522,8 @@ png_get_cHRM(png_const_structrp png_ptr, png_const_inforp info_ptr,
     double *white_x, double *white_y, double *red_x, double *red_y,
     double *green_x, double *green_y, double *blue_x, double *blue_y)
 {
+   png_debug1(1, "in %s retrieval function", "cHRM");
+
    /* Quiet API change: this code used to only return the end points if a cHRM
     * chunk was present, but the end points can also come from iCCP or sRGB
     * chunks, so in 1.6.0 the png_get_ APIs return the end points regardless and
@@ -533,8 +533,6 @@ png_get_cHRM(png_const_structrp png_ptr, png_const_inforp info_ptr,
    if (png_ptr != NULL && info_ptr != NULL &&
       (info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0)
    {
-      png_debug1(1, "in %s retrieval function", "cHRM");
-
       if (white_x != NULL)
          *white_x = png_float(png_ptr,
              info_ptr->colorspace.end_points_xy.whitex, "cHRM white X");
@@ -571,11 +569,11 @@ png_get_cHRM_XYZ(png_const_structrp png_ptr, png_const_inforp info_ptr,
     double *green_Y, double *green_Z, double *blue_X, double *blue_Y,
     double *blue_Z)
 {
+   png_debug1(1, "in %s retrieval function", "cHRM_XYZ(float)");
+
    if (png_ptr != NULL && info_ptr != NULL &&
        (info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0)
    {
-      png_debug1(1, "in %s retrieval function", "cHRM_XYZ(float)");
-
       if (red_X != NULL)
          *red_X = png_float(png_ptr, info_ptr->colorspace.end_points_XYZ.red_X,
              "cHRM red X");
@@ -619,11 +617,11 @@ png_get_cHRM_XYZ_fixed(png_const_structrp png_ptr, png_const_inforp info_ptr,
     png_fixed_point *int_blue_X, png_fixed_point *int_blue_Y,
     png_fixed_point *int_blue_Z)
 {
+   png_debug1(1, "in %s retrieval function", "cHRM_XYZ");
+
    if (png_ptr != NULL && info_ptr != NULL &&
       (info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0)
    {
-      png_debug1(1, "in %s retrieval function", "cHRM_XYZ");
-
       if (int_red_X != NULL)
          *int_red_X = info_ptr->colorspace.end_points_XYZ.red_X;
       if (int_red_Y != NULL)
@@ -775,6 +773,8 @@ int PNGAPI
 png_get_sPLT(png_const_structrp png_ptr, png_inforp info_ptr,
     png_sPLT_tpp spalettes)
 {
+   png_debug1(1, "in %s retrieval function", "sPLT");
+
    if (png_ptr != NULL && info_ptr != NULL && spalettes != NULL)
    {
       *spalettes = info_ptr->splt_palettes;
@@ -932,6 +932,8 @@ png_uint_32 PNGAPI
 png_get_sCAL_fixed(png_const_structrp png_ptr, png_const_inforp info_ptr,
     int *unit, png_fixed_point *width, png_fixed_point *height)
 {
+   png_debug1(1, "in %s retrieval function", "sCAL");
+
    if (png_ptr != NULL && info_ptr != NULL &&
        (info_ptr->valid & PNG_INFO_sCAL) != 0)
    {
@@ -955,6 +957,8 @@ png_uint_32 PNGAPI
 png_get_sCAL(png_const_structrp png_ptr, png_const_inforp info_ptr,
     int *unit, double *width, double *height)
 {
+   png_debug1(1, "in %s retrieval function", "sCAL(float)");
+
    if (png_ptr != NULL && info_ptr != NULL &&
        (info_ptr->valid & PNG_INFO_sCAL) != 0)
    {
@@ -971,6 +975,8 @@ png_uint_32 PNGAPI
 png_get_sCAL_s(png_const_structrp png_ptr, png_const_inforp info_ptr,
     int *unit, png_charpp width, png_charpp height)
 {
+   png_debug1(1, "in %s retrieval function", "sCAL(str)");
+
    if (png_ptr != NULL && info_ptr != NULL &&
        (info_ptr->valid & PNG_INFO_sCAL) != 0)
    {
@@ -1062,7 +1068,7 @@ png_get_text(png_const_structrp png_ptr, png_inforp info_ptr,
 {
    if (png_ptr != NULL && info_ptr != NULL && info_ptr->num_text > 0)
    {
-      png_debug1(1, "in 0x%lx retrieval function",
+      png_debug1(1, "in text retrieval function, chunk typeid = 0x%lx",
          (unsigned long)png_ptr->chunk_name);
 
       if (text_ptr != NULL)
@@ -1105,11 +1111,12 @@ png_get_tRNS(png_const_structrp png_ptr, png_inforp info_ptr,
     png_bytep *trans_alpha, int *num_trans, png_color_16p *trans_color)
 {
    png_uint_32 retval = 0;
+
+   png_debug1(1, "in %s retrieval function", "tRNS");
+
    if (png_ptr != NULL && info_ptr != NULL &&
        (info_ptr->valid & PNG_INFO_tRNS) != 0)
    {
-      png_debug1(1, "in %s retrieval function", "tRNS");
-
       if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
       {
          if (trans_alpha != NULL)

pngread.c

@@ -1,7 +1,7 @@
 
 /* pngread.c - read a PNG file
  *
- * Copyright (c) 2018-2019 Cosmin Truta
+ * Copyright (c) 2018-2024 Cosmin Truta
  * Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson
  * Copyright (c) 1996-1997 Andreas Dilger
  * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
@@ -1049,6 +1049,8 @@ void PNGAPI
 png_read_png(png_structrp png_ptr, png_inforp info_ptr,
     int transforms, voidp params)
 {
+   png_debug(1, "in png_read_png");
+
    if (png_ptr == NULL || info_ptr == NULL)
       return;
 

pngrtran.c

@@ -1,7 +1,7 @@
 
 /* pngrtran.c - transforms the data in a row for PNG readers
  *
- * Copyright (c) 2018-2019 Cosmin Truta
+ * Copyright (c) 2018-2024 Cosmin Truta
  * Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson
  * Copyright (c) 1996-1997 Andreas Dilger
  * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
@@ -290,7 +290,7 @@ png_set_alpha_mode_fixed(png_structrp png_ptr, int mode,
    int compose = 0;
    png_fixed_point file_gamma;
 
-   png_debug(1, "in png_set_alpha_mode");
+   png_debug(1, "in png_set_alpha_mode_fixed");
 
    if (png_rtran_ok(png_ptr, 0) == 0)
       return;
@@ -970,7 +970,7 @@ void PNGFAPI
 png_set_rgb_to_gray_fixed(png_structrp png_ptr, int error_action,
     png_fixed_point red, png_fixed_point green)
 {
-   png_debug(1, "in png_set_rgb_to_gray");
+   png_debug(1, "in png_set_rgb_to_gray_fixed");
 
    /* Need the IHDR here because of the check on color_type below. */
    /* TODO: fix this */

pngrutil.c

@@ -1,7 +1,7 @@
 
 /* pngrutil.c - utilities to read a PNG file
  *
- * Copyright (c) 2018-2022 Cosmin Truta
+ * Copyright (c) 2018-2024 Cosmin Truta
  * Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson
  * Copyright (c) 1996-1997 Andreas Dilger
  * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
@@ -171,7 +171,7 @@ png_read_chunk_header(png_structrp png_ptr)
    /* Put the chunk name into png_ptr->chunk_name. */
    png_ptr->chunk_name = PNG_CHUNK_FROM_STRING(buf+4);
 
-   png_debug2(0, "Reading %lx chunk, length = %lu",
+   png_debug2(0, "Reading chunk typeid = 0x%lx, length = %lu",
        (unsigned long)png_ptr->chunk_name, (unsigned long)length);
 
    /* Reset the crc and run it over the chunk name. */

pngset.c

@@ -1,7 +1,7 @@
 
 /* pngset.c - storage of image information into info struct
  *
- * Copyright (c) 2018-2023 Cosmin Truta
+ * Copyright (c) 2018-2024 Cosmin Truta
  * Copyright (c) 1998-2018 Glenn Randers-Pehrson
  * Copyright (c) 1996-1997 Andreas Dilger
  * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
@@ -763,8 +763,8 @@ png_set_text_2(png_const_structrp png_ptr, png_inforp info_ptr,
 {
    int i;
 
-   png_debug1(1, "in %lx storage function", png_ptr == NULL ? 0xabadca11U :
+   png_debug1(1, "in text storage function, chunk typeid = 0x%lx",
-      (unsigned long)png_ptr->chunk_name);
+      png_ptr == NULL ? 0xabadca11UL : (unsigned long)png_ptr->chunk_name);
 
    if (png_ptr == NULL || info_ptr == NULL || num_text <= 0 || text_ptr == NULL)
       return(0);
@@ -1063,6 +1063,8 @@ png_set_sPLT(png_const_structrp png_ptr,
 {
    png_sPLT_tp np;
 
+   png_debug1(1, "in %s storage function", "sPLT");
+
    if (png_ptr == NULL || info_ptr == NULL || nentries <= 0 || entries == NULL)
       return;
 
@@ -1537,7 +1539,7 @@ void PNGAPI
 png_set_rows(png_const_structrp png_ptr, png_inforp info_ptr,
     png_bytepp row_pointers)
 {
-   png_debug1(1, "in %s storage function", "rows");
+   png_debug(1, "in png_set_rows");
 
    if (png_ptr == NULL || info_ptr == NULL)
       return;
@@ -1556,6 +1558,8 @@ png_set_rows(png_const_structrp png_ptr, png_inforp info_ptr,
 void PNGAPI
 png_set_compression_buffer_size(png_structrp png_ptr, size_t size)
 {
+   png_debug(1, "in png_set_compression_buffer_size");
+
    if (png_ptr == NULL)
       return;
 
@@ -1627,6 +1631,8 @@ void PNGAPI
 png_set_user_limits(png_structrp png_ptr, png_uint_32 user_width_max,
     png_uint_32 user_height_max)
 {
+   png_debug(1, "in png_set_user_limits");
+
    /* Images with dimensions larger than these limits will be
     * rejected by png_set_IHDR().  To accept any PNG datastream
     * regardless of dimensions, set both limits to 0x7fffffff.
@@ -1642,6 +1648,8 @@ png_set_user_limits(png_structrp png_ptr, png_uint_32 user_width_max,
 void PNGAPI
 png_set_chunk_cache_max(png_structrp png_ptr, png_uint_32 user_chunk_cache_max)
 {
+   png_debug(1, "in png_set_chunk_cache_max");
+
    if (png_ptr != NULL)
       png_ptr->user_chunk_cache_max = user_chunk_cache_max;
 }
@@ -1651,6 +1659,8 @@ void PNGAPI
 png_set_chunk_malloc_max(png_structrp png_ptr,
     png_alloc_size_t user_chunk_malloc_max)
 {
+   png_debug(1, "in png_set_chunk_malloc_max");
+
    if (png_ptr != NULL)
       png_ptr->user_chunk_malloc_max = user_chunk_malloc_max;
 }

pngtest.c

@@ -1,7 +1,7 @@
 
 /* pngtest.c - a simple test program to test libpng
  *
- * Copyright (c) 2018-2023 Cosmin Truta
+ * Copyright (c) 2018-2024 Cosmin Truta
  * Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson
  * Copyright (c) 1996-1997 Andreas Dilger
  * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
@@ -1656,16 +1656,16 @@ test_one_file(const char *inname, const char *outname)
 
    pngtest_debug("Destroying data structs");
 #ifdef SINGLE_ROWBUF_ALLOC
-   pngtest_debug("destroying row_buf for read_ptr");
+   pngtest_debug("Destroying row_buf for read_ptr");
    png_free(read_ptr, row_buf);
    row_buf = NULL;
 #endif /* SINGLE_ROWBUF_ALLOC */
-   pngtest_debug("destroying read_ptr, read_info_ptr, end_info_ptr");
+   pngtest_debug("Destroying read_ptr, read_info_ptr, end_info_ptr");
    png_destroy_read_struct(&read_ptr, &read_info_ptr, &end_info_ptr);
 #ifdef PNG_WRITE_SUPPORTED
-   pngtest_debug("destroying write_end_info_ptr");
+   pngtest_debug("Destroying write_end_info_ptr");
    png_destroy_info_struct(write_ptr, &write_end_info_ptr);
-   pngtest_debug("destroying write_ptr, write_info_ptr");
+   pngtest_debug("Destroying write_ptr, write_info_ptr");
    png_destroy_write_struct(&write_ptr, &write_info_ptr);
 #endif
    pngtest_debug("Destruction complete.");

pngtrans.c

@@ -1,7 +1,7 @@
 
 /* pngtrans.c - transforms the data in a row (used by both readers and writers)
  *
- * Copyright (c) 2018 Cosmin Truta
+ * Copyright (c) 2018-2024 Cosmin Truta
  * Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson
  * Copyright (c) 1996-1997 Andreas Dilger
  * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
@@ -498,6 +498,8 @@ png_do_strip_channel(png_row_infop row_info, png_bytep row, int at_start)
    png_bytep dp = row; /* destination pointer */
    png_bytep ep = row + row_info->rowbytes; /* One beyond end of row */
 
+   png_debug(1, "in png_do_strip_channel");
+
    /* At the start sp will point to the first byte to copy and dp to where
     * it is copied to.  ep always points just beyond the end of the row, so
     * the loop simply copies (channels-1) channels until sp reaches ep.
@@ -698,6 +700,8 @@ png_do_bgr(png_row_infop row_info, png_bytep row)
 void /* PRIVATE */
 png_do_check_palette_indexes(png_structrp png_ptr, png_row_infop row_info)
 {
+   png_debug(1, "in png_do_check_palette_indexes");
+
    if (png_ptr->num_palette < (1 << row_info->bit_depth) &&
       png_ptr->num_palette > 0) /* num_palette can be 0 in MNG files */
    {

pngwrite.c

@@ -1,7 +1,7 @@
 
 /* pngwrite.c - general routines to write a PNG file
  *
- * Copyright (c) 2018-2023 Cosmin Truta
+ * Copyright (c) 2018-2024 Cosmin Truta
  * Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson
  * Copyright (c) 1996-1997 Andreas Dilger
  * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
@@ -715,12 +715,12 @@ png_write_row(png_structrp png_ptr, png_const_bytep row)
    /* 1.5.6: moved from png_struct to be a local structure: */
    png_row_info row_info;
 
-   if (png_ptr == NULL)
-      return;
-
    png_debug2(1, "in png_write_row (row %u, pass %d)",
        png_ptr->row_number, png_ptr->pass);
 
+   if (png_ptr == NULL)
+      return;
+
    /* Initialize transformations and other stuff if first time */
    if (png_ptr->row_number == 0 && png_ptr->pass == 0)
    {
@@ -1211,6 +1211,8 @@ png_set_compression_strategy(png_structrp png_ptr, int strategy)
 void PNGAPI
 png_set_compression_window_bits(png_structrp png_ptr, int window_bits)
 {
+   png_debug(1, "in png_set_compression_window_bits");
+
    if (png_ptr == NULL)
       return;
 
@@ -1294,6 +1296,8 @@ png_set_text_compression_strategy(png_structrp png_ptr, int strategy)
 void PNGAPI
 png_set_text_compression_window_bits(png_structrp png_ptr, int window_bits)
 {
+   png_debug(1, "in png_set_text_compression_window_bits");
+
    if (png_ptr == NULL)
       return;
 
@@ -1331,6 +1335,8 @@ png_set_text_compression_method(png_structrp png_ptr, int method)
 void PNGAPI
 png_set_write_status_fn(png_structrp png_ptr, png_write_status_ptr write_row_fn)
 {
+   png_debug(1, "in png_set_write_status_fn");
+
    if (png_ptr == NULL)
       return;
 
@@ -1358,6 +1364,8 @@ void PNGAPI
 png_write_png(png_structrp png_ptr, png_inforp info_ptr,
     int transforms, voidp params)
 {
+   png_debug(1, "in png_write_png");
+
    if (png_ptr == NULL || info_ptr == NULL)
       return;