diff --git a/libavutil/adler32.h b/libavutil/adler32.h
index 2e29e05b25..91dff9a4ec 100644
--- a/libavutil/adler32.h
+++ b/libavutil/adler32.h
@@ -24,6 +24,6 @@
 #include <stdint.h>
 
 unsigned long av_adler32_update(unsigned long adler, const uint8_t *buf,
-                                unsigned int len);
+                                unsigned int len) av_pure;
 
 #endif /* FFMPEG_ADLER32_H */
diff --git a/libavutil/bswap.h b/libavutil/bswap.h
index 64ac5d2384..b35fb51613 100644
--- a/libavutil/bswap.h
+++ b/libavutil/bswap.h
@@ -34,7 +34,7 @@
 #include <byteswap.h>
 #else
 
-static av_always_inline uint16_t bswap_16(uint16_t x)
+static av_always_inline av_const uint16_t bswap_16(uint16_t x)
 {
 #if defined(ARCH_X86)
     asm("rorw $8, %0" : "+r"(x));
@@ -46,7 +46,7 @@ static av_always_inline uint16_t bswap_16(uint16_t x)
     return x;
 }
 
-static av_always_inline uint32_t bswap_32(uint32_t x)
+static av_always_inline av_const uint32_t bswap_32(uint32_t x)
 {
 #if defined(ARCH_X86)
 #ifdef HAVE_BSWAP
@@ -83,7 +83,7 @@ static av_always_inline uint32_t bswap_32(uint32_t x)
     return x;
 }
 
-static inline uint64_t bswap_64(uint64_t x)
+static inline uint64_t av_const bswap_64(uint64_t x)
 {
 #if 0
     x= ((x<< 8)&0xFF00FF00FF00FF00ULL) | ((x>> 8)&0x00FF00FF00FF00FFULL);
diff --git a/libavutil/common.h b/libavutil/common.h
index fd1d00c7b3..d2489e3f32 100644
--- a/libavutil/common.h
+++ b/libavutil/common.h
@@ -57,6 +57,22 @@
 #endif
 #endif
 
+#ifndef av_pure
+#if defined(__GNUC__) && (__GNUC__ > 3 || __GNUC__ == 3 && __GNUC_MINOR__ > 0)
+#    define av_pure __attribute__((pure))
+#else
+#    define av_pure
+#endif
+#endif
+
+#ifndef av_const
+#if defined(__GNUC__) && (__GNUC__ > 2 || __GNUC__ == 2 && __GNUC_MINOR__ > 5)
+#    define av_const __attribute__((const))
+#else
+#    define av_const
+#endif
+#endif
+
 #ifdef HAVE_AV_CONFIG_H
 #    include "internal.h"
 #endif /* HAVE_AV_CONFIG_H */
@@ -94,7 +110,7 @@
 /* misc math functions */
 extern const uint8_t ff_log2_tab[256];
 
-static inline int av_log2(unsigned int v)
+static inline av_const int av_log2(unsigned int v)
 {
     int n = 0;
     if (v & 0xffff0000) {
@@ -110,7 +126,7 @@ static inline int av_log2(unsigned int v)
     return n;
 }
 
-static inline int av_log2_16bit(unsigned int v)
+static inline av_const int av_log2_16bit(unsigned int v)
 {
     int n = 0;
     if (v & 0xff00) {
@@ -123,7 +139,7 @@ static inline int av_log2_16bit(unsigned int v)
 }
 
 /* median of 3 */
-static inline int mid_pred(int a, int b, int c)
+static inline av_const int mid_pred(int a, int b, int c)
 {
 #ifdef HAVE_CMOV
     int i=b;
@@ -170,7 +186,7 @@ static inline int mid_pred(int a, int b, int c)
  * @param amax maximum value of the clip range
  * @return clipped value
  */
-static inline int av_clip(int a, int amin, int amax)
+static inline av_const int av_clip(int a, int amin, int amax)
 {
     if      (a < amin) return amin;
     else if (a > amax) return amax;
@@ -182,7 +198,7 @@ static inline int av_clip(int a, int amin, int amax)
  * @param a value to clip
  * @return clipped value
  */
-static inline uint8_t av_clip_uint8(int a)
+static inline av_const uint8_t av_clip_uint8(int a)
 {
     if (a&(~255)) return (-a)>>31;
     else          return a;
@@ -193,19 +209,19 @@ static inline uint8_t av_clip_uint8(int a)
  * @param a value to clip
  * @return clipped value
  */
-static inline int16_t av_clip_int16(int a)
+static inline av_const int16_t av_clip_int16(int a)
 {
     if ((a+32768) & ~65535) return (a>>31) ^ 32767;
     else                    return a;
 }
 
 /* math */
-int64_t ff_gcd(int64_t a, int64_t b);
+int64_t av_const ff_gcd(int64_t a, int64_t b);
 
 /**
  * converts fourcc string to int
  */
-static inline int ff_get_fourcc(const char *s){
+static inline av_pure int ff_get_fourcc(const char *s){
 #ifdef HAVE_AV_CONFIG_H
     assert( strlen(s)==4 );
 #endif
diff --git a/libavutil/crc.h b/libavutil/crc.h
index d6b93c38d2..9798cf6a38 100644
--- a/libavutil/crc.h
+++ b/libavutil/crc.h
@@ -37,7 +37,7 @@ typedef enum {
 
 int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size);
 const AVCRC *av_crc_get_table(AVCRCId crc_id);
-uint32_t av_crc(const AVCRC *ctx, uint32_t start_crc, const uint8_t *buffer, size_t length);
+uint32_t av_crc(const AVCRC *ctx, uint32_t start_crc, const uint8_t *buffer, size_t length) av_pure;
 
 #endif /* FFMPEG_CRC_H */
 
diff --git a/libavutil/des.c b/libavutil/des.c
index 36f90ffaae..d1e47f4576 100644
--- a/libavutil/des.c
+++ b/libavutil/des.c
@@ -19,6 +19,7 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 #include <inttypes.h>
+#include "common.h"
 #include "des.h"
 
 #define T(a, b, c, d, e, f, g, h) 64-a,64-b,64-c,64-d,64-e,64-f,64-g,64-h
diff --git a/libavutil/des.h b/libavutil/des.h
index 70f89937c1..26a40dc0c1 100644
--- a/libavutil/des.h
+++ b/libavutil/des.h
@@ -34,6 +34,6 @@
  * If your input data is in 8-bit blocks treat it as big-endian
  * (use e.g. AV_RB64 and AV_WB64).
  */
-uint64_t ff_des_encdec(uint64_t in, uint64_t key, int decrypt);
+uint64_t ff_des_encdec(uint64_t in, uint64_t key, int decrypt) av_const;
 
 #endif /* FFMPEG_DES_H */
diff --git a/libavutil/integer.h b/libavutil/integer.h
index f539125d14..9e85eb97ab 100644
--- a/libavutil/integer.h
+++ b/libavutil/integer.h
@@ -36,26 +36,26 @@ typedef struct AVInteger{
     uint16_t v[AV_INTEGER_SIZE];
 } AVInteger;
 
-AVInteger av_add_i(AVInteger a, AVInteger b);
-AVInteger av_sub_i(AVInteger a, AVInteger b);
+AVInteger av_add_i(AVInteger a, AVInteger b) av_const;
+AVInteger av_sub_i(AVInteger a, AVInteger b) av_const;
 
 /**
  * returns the rounded down value of the logarithm of base 2 of the given AVInteger.
  * this is simply the index of the most significant bit which is 1. Or 0 of all bits are 0
  */
-int av_log2_i(AVInteger a);
-AVInteger av_mul_i(AVInteger a, AVInteger b);
+int av_log2_i(AVInteger a) av_const;
+AVInteger av_mul_i(AVInteger a, AVInteger b) av_const;
 
 /**
  * returns 0 if a==b, 1 if a>b and -1 if a<b.
  */
-int av_cmp_i(AVInteger a, AVInteger b);
+int av_cmp_i(AVInteger a, AVInteger b) av_const;
 
 /**
  * bitwise shift.
  * @param s the number of bits by which the value should be shifted right, may be negative for shifting left
  */
-AVInteger av_shr_i(AVInteger a, int s);
+AVInteger av_shr_i(AVInteger a, int s) av_const;
 
 /**
  * returns a % b.
@@ -66,18 +66,18 @@ AVInteger av_mod_i(AVInteger *quot, AVInteger a, AVInteger b);
 /**
  * returns a/b.
  */
-AVInteger av_div_i(AVInteger a, AVInteger b);
+AVInteger av_div_i(AVInteger a, AVInteger b) av_const;
 
 /**
  * converts the given int64_t to an AVInteger.
  */
-AVInteger av_int2i(int64_t a);
+AVInteger av_int2i(int64_t a) av_const;
 
 /**
  * converts the given AVInteger to an int64_t.
  * if the AVInteger is too large to fit into an int64_t,
  * then only the least significant 64bit will be used
  */
-int64_t av_i2int(AVInteger a);
+int64_t av_i2int(AVInteger a) av_const;
 
 #endif /* FFMPEG_INTEGER_H */
diff --git a/libavutil/internal.h b/libavutil/internal.h
index ccb0974ad2..66a136de68 100644
--- a/libavutil/internal.h
+++ b/libavutil/internal.h
@@ -172,7 +172,7 @@ extern const uint8_t ff_sqrt_tab[256];
 
 static inline int av_log2_16bit(unsigned int v);
 
-static inline unsigned int ff_sqrt(unsigned int a)
+static inline av_const unsigned int ff_sqrt(unsigned int a)
 {
     unsigned int b;
 
@@ -267,35 +267,35 @@ if((y)<(x)){\
 }
 
 #ifndef HAVE_LLRINT
-static av_always_inline long long llrint(double x)
+static av_always_inline av_const long long llrint(double x)
 {
     return rint(x);
 }
 #endif /* HAVE_LLRINT */
 
 #ifndef HAVE_LRINT
-static av_always_inline long int lrint(double x)
+static av_always_inline av_const long int lrint(double x)
 {
     return rint(x);
 }
 #endif /* HAVE_LRINT */
 
 #ifndef HAVE_LRINTF
-static av_always_inline long int lrintf(float x)
+static av_always_inline av_const long int lrintf(float x)
 {
     return (int)(rint(x));
 }
 #endif /* HAVE_LRINTF */
 
 #ifndef HAVE_ROUND
-static av_always_inline double round(double x)
+static av_always_inline av_const double round(double x)
 {
     return (x > 0) ? floor(x + 0.5) : ceil(x - 0.5);
 }
 #endif /* HAVE_ROUND */
 
 #ifndef HAVE_ROUNDF
-static av_always_inline float roundf(float x)
+static av_always_inline av_const float roundf(float x)
 {
     return (x > 0) ? floor(x + 0.5) : ceil(x - 0.5);
 }
diff --git a/libavutil/intfloat_readwrite.h b/libavutil/intfloat_readwrite.h
index 1ebb053f3a..4b3f9b7bcf 100644
--- a/libavutil/intfloat_readwrite.h
+++ b/libavutil/intfloat_readwrite.h
@@ -30,11 +30,11 @@ typedef struct AVExtFloat  {
     uint8_t mantissa[8];
 } AVExtFloat;
 
-double av_int2dbl(int64_t v);
-float av_int2flt(int32_t v);
-double av_ext2dbl(const AVExtFloat ext);
-int64_t av_dbl2int(double d);
-int32_t av_flt2int(float d);
-AVExtFloat av_dbl2ext(double d);
+double av_int2dbl(int64_t v) av_const;
+float av_int2flt(int32_t v) av_const;
+double av_ext2dbl(const AVExtFloat ext) av_const;
+int64_t av_dbl2int(double d) av_const;
+int32_t av_flt2int(float d) av_const;
+AVExtFloat av_dbl2ext(double d) av_const;
 
 #endif /* FFMPEG_INTFLOAT_READWRITE_H */
diff --git a/libavutil/mathematics.h b/libavutil/mathematics.h
index fa407b6111..a9dfe7eccf 100644
--- a/libavutil/mathematics.h
+++ b/libavutil/mathematics.h
@@ -36,17 +36,17 @@ enum AVRounding {
  * rescale a 64bit integer with rounding to nearest.
  * a simple a*b/c isn't possible as it can overflow
  */
-int64_t av_rescale(int64_t a, int64_t b, int64_t c);
+int64_t av_rescale(int64_t a, int64_t b, int64_t c) av_const;
 
 /**
  * rescale a 64bit integer with specified rounding.
  * a simple a*b/c isn't possible as it can overflow
  */
-int64_t av_rescale_rnd(int64_t a, int64_t b, int64_t c, enum AVRounding);
+int64_t av_rescale_rnd(int64_t a, int64_t b, int64_t c, enum AVRounding) av_const;
 
 /**
  * rescale a 64bit integer by 2 rational numbers.
  */
-int64_t av_rescale_q(int64_t a, AVRational bq, AVRational cq);
+int64_t av_rescale_q(int64_t a, AVRational bq, AVRational cq) av_const;
 
 #endif /* FFMPEG_MATHEMATICS_H */
diff --git a/libavutil/mem.h b/libavutil/mem.h
index f8df42cfe7..c68117d43d 100644
--- a/libavutil/mem.h
+++ b/libavutil/mem.h
@@ -42,6 +42,12 @@
     #define DECLARE_ASM_CONST(n,t,v)    static const t v
 #endif
 
+#ifdef __GNUC__
+    #define av_malloc_attrib __attribute__((__malloc__))
+#else
+    #define av_malloc_attrib
+#endif
+
 /**
  * Allocate a block of \p size bytes with alignment suitable for all
  * memory accesses (including vectors if available on the CPU).
@@ -50,7 +56,7 @@
  * it.
  * @see av_mallocz()
  */
-void *av_malloc(unsigned int size);
+void *av_malloc(unsigned int size) av_malloc_attrib;
 
 /**
  * Allocate or reallocate a block of memory.
@@ -85,7 +91,7 @@ void av_free(void *ptr);
  * it.
  * @see av_malloc()
  */
-void *av_mallocz(unsigned int size);
+void *av_mallocz(unsigned int size) av_malloc_attrib;
 
 /**
  * Duplicate the string \p s.
@@ -93,7 +99,7 @@ void *av_mallocz(unsigned int size);
  * @return Pointer to a newly allocated string containing a
  * copy of \p s or NULL if it cannot be allocated.
  */
-char *av_strdup(const char *s);
+char *av_strdup(const char *s) av_malloc_attrib;
 
 /**
  * Free a memory block which has been allocated with av_malloc(z)() or
diff --git a/libavutil/rational.h b/libavutil/rational.h
index f53f278619..2f0017c868 100644
--- a/libavutil/rational.h
+++ b/libavutil/rational.h
@@ -29,6 +29,7 @@
 #define FFMPEG_RATIONAL_H
 
 #include <stdint.h>
+#include "common.h"
 
 /**
  * Rational number num/den.
@@ -78,7 +79,7 @@ int av_reduce(int *dst_nom, int *dst_den, int64_t nom, int64_t den, int64_t max)
  * @param c second rational.
  * @return b*c.
  */
-AVRational av_mul_q(AVRational b, AVRational c);
+AVRational av_mul_q(AVRational b, AVRational c) av_const;
 
 /**
  * Divides one rational by another.
@@ -86,7 +87,7 @@ AVRational av_mul_q(AVRational b, AVRational c);
  * @param c second rational.
  * @return b/c.
  */
-AVRational av_div_q(AVRational b, AVRational c);
+AVRational av_div_q(AVRational b, AVRational c) av_const;
 
 /**
  * Adds two rationals.
@@ -94,7 +95,7 @@ AVRational av_div_q(AVRational b, AVRational c);
  * @param c second rational.
  * @return b+c.
  */
-AVRational av_add_q(AVRational b, AVRational c);
+AVRational av_add_q(AVRational b, AVRational c) av_const;
 
 /**
  * Subtracts one rational from another.
@@ -102,7 +103,7 @@ AVRational av_add_q(AVRational b, AVRational c);
  * @param c second rational.
  * @return b-c.
  */
-AVRational av_sub_q(AVRational b, AVRational c);
+AVRational av_sub_q(AVRational b, AVRational c) av_const;
 
 /**
  * Converts a double precision floating point number to a rational.
@@ -110,6 +111,6 @@ AVRational av_sub_q(AVRational b, AVRational c);
  * @param max the maximum allowed numerator and denominator
  * @return (AVRational) d.
  */
-AVRational av_d2q(double d, int max);
+AVRational av_d2q(double d, int max) av_const;
 
 #endif /* FFMPEG_RATIONAL_H */
diff --git a/libavutil/softfloat.h b/libavutil/softfloat.h
index d1a1901ea5..bb8bb279be 100644
--- a/libavutil/softfloat.h
+++ b/libavutil/softfloat.h
@@ -32,7 +32,7 @@ typedef struct SoftFloat{
     int32_t mant;
 }SoftFloat;
 
-static SoftFloat av_normalize_sf(SoftFloat a){
+static av_const SoftFloat av_normalize_sf(SoftFloat a){
     if(a.mant){
 #if 1
         while((a.mant + 0x20000000U)<0x40000000U){
@@ -54,7 +54,7 @@ static SoftFloat av_normalize_sf(SoftFloat a){
     return a;
 }
 
-static inline SoftFloat av_normalize1_sf(SoftFloat a){
+static inline av_const SoftFloat av_normalize1_sf(SoftFloat a){
 #if 1
     if(a.mant + 0x40000000 < 0){
         a.exp++;
@@ -76,7 +76,7 @@ static inline SoftFloat av_normalize1_sf(SoftFloat a){
  *         normalized then the output wont be worse then the other input
  *         if both are normalized then the output will be normalized
  */
-static inline SoftFloat av_mul_sf(SoftFloat a, SoftFloat b){
+static inline av_const SoftFloat av_mul_sf(SoftFloat a, SoftFloat b){
     a.exp += b.exp;
     a.mant = (a.mant * (int64_t)b.mant) >> ONE_BITS;
     return av_normalize1_sf(a);
@@ -87,31 +87,31 @@ static inline SoftFloat av_mul_sf(SoftFloat a, SoftFloat b){
  * b has to be normalized and not zero
  * @return will not be more denormalized then a
  */
-static SoftFloat av_div_sf(SoftFloat a, SoftFloat b){
+static av_const SoftFloat av_div_sf(SoftFloat a, SoftFloat b){
     a.exp -= b.exp+1;
     a.mant = ((int64_t)a.mant<<(ONE_BITS+1)) / b.mant;
     return av_normalize1_sf(a);
 }
 
-static inline int av_cmp_sf(SoftFloat a, SoftFloat b){
+static inline av_const int av_cmp_sf(SoftFloat a, SoftFloat b){
     int t= a.exp - b.exp;
     if(t<0) return (a.mant >> (-t)) -  b.mant      ;
     else    return  a.mant          - (b.mant >> t);
 }
 
-static inline SoftFloat av_add_sf(SoftFloat a, SoftFloat b){
+static inline av_const SoftFloat av_add_sf(SoftFloat a, SoftFloat b){
     int t= a.exp - b.exp;
     if(t<0) return av_normalize1_sf((SoftFloat){b.exp, b.mant + (a.mant >> (-t))});
     else    return av_normalize1_sf((SoftFloat){a.exp, a.mant + (b.mant >>   t )});
 }
 
-static inline SoftFloat av_sub_sf(SoftFloat a, SoftFloat b){
+static inline av_const SoftFloat av_sub_sf(SoftFloat a, SoftFloat b){
     return av_add_sf(a, (SoftFloat){b.exp, -b.mant});
 }
 
 //FIXME sqrt, log, exp, pow, sin, cos
 
-static inline SoftFloat av_int2sf(int v, int frac_bits){
+static inline av_const SoftFloat av_int2sf(int v, int frac_bits){
     return av_normalize_sf((SoftFloat){ONE_BITS-frac_bits, v});
 }
 
@@ -119,7 +119,7 @@ static inline SoftFloat av_int2sf(int v, int frac_bits){
  *
  * rounding is to -inf
  */
-static inline int av_sf2int(SoftFloat v, int frac_bits){
+static inline av_const int av_sf2int(SoftFloat v, int frac_bits){
     v.exp += frac_bits - ONE_BITS;
     if(v.exp >= 0) return v.mant <<  v.exp ;
     else           return v.mant >>(-v.exp);