Fix clang unused function compile warnings

stb_image.h

@@ -105,7 +105,7 @@ RECENT REVISION HISTORY:
     Oriol Ferrer Mesia      Josh Tobin         Matthew Gregan     github:phprus
     Julian Raschke          Gregory Mullen     Baldur Karlsson    github:poppolopoppo
     Christian Floisand      Kevin Schmidt      JR Smith           github:darealshinji
-    Blazej Dariusz Roszkowski                                     github:Michaelangel007
+    Brad Weinberger         Blazej Dariusz Roszkowski             github:Michaelangel007
 */
 
 #ifndef STBI_INCLUDE_STB_IMAGE_H
@@ -924,11 +924,13 @@ static int stbi__mul2sizes_valid(int a, int b)
    return a <= INT_MAX/b;
 }
 
+#if !defined(STBI_NO_JPEG) || !defined(STBI_NO_PNG) || !defined(STBI_NO_TGA) || !defined(STBI_NO_HDR)
 // returns 1 if "a*b + add" has no negative terms/factors and doesn't overflow
 static int stbi__mad2sizes_valid(int a, int b, int add)
 {
    return stbi__mul2sizes_valid(a, b) && stbi__addsizes_valid(a*b, add);
 }
+#endif
 
 // returns 1 if "a*b*c + add" has no negative terms/factors and doesn't overflow
 static int stbi__mad3sizes_valid(int a, int b, int c, int add)
@@ -946,12 +948,14 @@ static int stbi__mad4sizes_valid(int a, int b, int c, int d, int add)
 }
 #endif
 
+#if !defined(STBI_NO_JPEG) || !defined(STBI_NO_PNG) || !defined(STBI_NO_TGA) || !defined(STBI_NO_HDR)
 // mallocs with size overflow checking
 static void *stbi__malloc_mad2(int a, int b, int add)
 {
    if (!stbi__mad2sizes_valid(a, b, add)) return NULL;
    return stbi__malloc(a*b + add);
 }
+#endif
 
 static void *stbi__malloc_mad3(int a, int b, int c, int add)
 {
@@ -1477,6 +1481,9 @@ stbi_inline static stbi_uc stbi__get8(stbi__context *s)
    return 0;
 }
 
+#if defined(STBI_NO_JPEG) && defined(STBI_NO_HDR) && defined(STBI_NO_PIC) && defined(STBI_NO_PNM)
+// nothing
+#else
 stbi_inline static int stbi__at_eof(stbi__context *s)
 {
    if (s->io.read) {
@@ -1488,7 +1495,11 @@ stbi_inline static int stbi__at_eof(stbi__context *s)
 
    return s->img_buffer >= s->img_buffer_end;
 }
+#endif
 
+#if defined(STBI_NO_JPEG) && defined(STBI_NO_PNG) && defined(STBI_NO_BMP) && defined(STBI_NO_PSD) && defined(STBI_NO_TGA) && defined(STBI_NO_GIF) && defined(STBI_NO_PIC)
+// nothing
+#else
 static void stbi__skip(stbi__context *s, int n)
 {
    if (n < 0) {
@@ -1505,7 +1516,11 @@ static void stbi__skip(stbi__context *s, int n)
    }
    s->img_buffer += n;
 }
+#endif
 
+#if defined(STBI_NO_PNG) && defined(STBI_NO_TGA) && defined(STBI_NO_HDR) && defined(STBI_NO_PNM)
+// nothing
+#else
 static int stbi__getn(stbi__context *s, stbi_uc *buffer, int n)
 {
    if (s->io.read) {
@@ -1529,18 +1544,27 @@ static int stbi__getn(stbi__context *s, stbi_uc *buffer, int n)
    } else
       return 0;
 }
+#endif
 
+#if defined(STBI_NO_JPEG) && defined(STBI_NO_PNG) && defined(STBI_NO_PSD) && defined(STBI_NO_PIC)
+// nothing
+#else
 static int stbi__get16be(stbi__context *s)
 {
    int z = stbi__get8(s);
    return (z << 8) + stbi__get8(s);
 }
+#endif
 
+#if defined(STBI_NO_PNG) && defined(STBI_NO_PSD) && defined(STBI_NO_PIC)
+// nothing
+#else
 static stbi__uint32 stbi__get32be(stbi__context *s)
 {
    stbi__uint32 z = stbi__get16be(s);
    return (z << 16) + stbi__get16be(s);
 }
+#endif
 
 #if defined(STBI_NO_BMP) && defined(STBI_NO_TGA) && defined(STBI_NO_GIF)
 // nothing
@@ -1562,7 +1586,9 @@ static stbi__uint32 stbi__get32le(stbi__context *s)
 
 #define STBI__BYTECAST(x)  ((stbi_uc) ((x) & 255))  // truncate int to byte without warnings
 
-
+#if defined(STBI_NO_JPEG) && defined(STBI_NO_PNG) && defined(STBI_NO_BMP) && defined(STBI_NO_PSD) && defined(STBI_NO_TGA) && defined(STBI_NO_GIF) && defined(STBI_NO_PIC) && defined(STBI_NO_PNM)
+// nothing
+#else
 //////////////////////////////////////////////////////////////////////////////
 //
 //  generic converter from built-in img_n to req_comp
@@ -1578,7 +1604,11 @@ static stbi_uc stbi__compute_y(int r, int g, int b)
 {
    return (stbi_uc) (((r*77) + (g*150) +  (29*b)) >> 8);
 }
+#endif
 
+#if defined(STBI_NO_PNG) && defined(STBI_NO_BMP) && defined(STBI_NO_PSD) && defined(STBI_NO_TGA) && defined(STBI_NO_GIF) && defined(STBI_NO_PIC) && defined(STBI_NO_PNM)
+// nothing
+#else
 static unsigned char *stbi__convert_format(unsigned char *data, int img_n, int req_comp, unsigned int x, unsigned int y)
 {
    int i,j;
@@ -1622,12 +1652,20 @@ static unsigned char *stbi__convert_format(unsigned char *data, int img_n, int r
    STBI_FREE(data);
    return good;
 }
+#endif
 
+#if defined(STBI_NO_PNG) && defined(STBI_NO_PSD)
+// nothing
+#else
 static stbi__uint16 stbi__compute_y_16(int r, int g, int b)
 {
    return (stbi__uint16) (((r*77) + (g*150) +  (29*b)) >> 8);
 }
+#endif
 
+#if defined(STBI_NO_PNG) && defined(STBI_NO_PSD)
+// nothing
+#else
 static stbi__uint16 *stbi__convert_format16(stbi__uint16 *data, int img_n, int req_comp, unsigned int x, unsigned int y)
 {
    int i,j;
@@ -1671,6 +1709,7 @@ static stbi__uint16 *stbi__convert_format16(stbi__uint16 *data, int img_n, int r
    STBI_FREE(data);
    return good;
 }
+#endif
 
 #ifndef STBI_NO_LINEAR
 static float   *stbi__ldr_to_hdr(stbi_uc *data, int x, int y, int comp)