diff --git a/Test/300layout.frag b/Test/300layout.frag
index b4b0bba5..70cbc9a5 100644
--- a/Test/300layout.frag
+++ b/Test/300layout.frag
@@ -13,3 +13,7 @@ void main()
     p = pos;
     q[1] = pos;
 }
+
+layout(location = 40) out float ca[4];
+layout(location = 41) out float cb[2];  // ERROR, overlap
+layout(location = 39) out float cc[6];  // ERROR, overlap
diff --git a/Test/300layout.vert b/Test/300layout.vert
index 18f69c3e..6a863cf5 100644
--- a/Test/300layout.vert
+++ b/Test/300layout.vert
@@ -5,7 +5,7 @@ struct s { vec4 v; };
 layout(location = 7) in vec3 c;
 layout(LocatioN = 3) in vec4 p;
 layout(LocatioN = 9) in vec4 q[4]; // ERROR, no array
-layout(LocatioN = 10) in s r[4];   // ERROR, no struct
+layout(LocatioN = 10) in s r[4];   // ERROR, no struct, ERROR, location overlap
 out vec4 pos;
 out vec3 color;
 
@@ -52,3 +52,6 @@ shared vec4 compute_only;  // ERROR
 layout(packed) uniform;
 
 layout(packed) float aoeuntaoeu;
+
+layout(location = 40) in float cd;
+layout(location = 37) in mat4x3 ce; // ERROR, overlap
diff --git a/Test/400.frag b/Test/400.frag
index c8039f0f..6d471389 100644
--- a/Test/400.frag
+++ b/Test/400.frag
@@ -33,7 +33,7 @@ layout(location = 4) in vec4 vl; // ERROR, not supported
 #extension GL_ARB_separate_shader_objects : enable
 #endif
 
-layout(location = 4) in vec4 vl2;
+layout(location = 6) in vec4 vl2;
 
 layout(location = 3) uniform vec3 uv3;
 
diff --git a/Test/430.vert b/Test/430.vert
index 6912fb4e..25c17a26 100644
--- a/Test/430.vert
+++ b/Test/430.vert
@@ -2,7 +2,7 @@
 
 layout(location = 3) vec4 v4;  // ERROR
 
-layout(location = 3) uniform vec4 uv4;
+layout(location = 4) uniform vec4 uv4;
 
 layout(location = 2) in   inb1 { vec4 v; } b1;  // ERROR
 layout(location = 2) out outb1 { vec4 v; } b2;  // ERROR
@@ -30,4 +30,13 @@ void foo3(invariant vec4 v4,                 // ERROR
           layout(location = 3) vec2 v2,      // ERROR
           centroid vec3 cv3)                 // ERROR
 {
-}
\ No newline at end of file
+}
+
+struct S {
+    mat3x2 m[7];  // needs 7*3 locations
+    float f;      // needs 1 location
+};                // needs 22 locations
+
+layout(location = 10) out S cs[2];     // 10 through 10 + 2 * 22 - 1 = 53
+layout(location = 54) out float cf;
+layout(location = 53) out float cg; // ERROR, collision at 31
diff --git a/Test/baseResults/300layout.frag.out b/Test/baseResults/300layout.frag.out
index 95d35963..ac665696 100644
--- a/Test/baseResults/300layout.frag.out
+++ b/Test/baseResults/300layout.frag.out
@@ -1,6 +1,8 @@
 300layout.frag
 ERROR: 0:4: 'location qualifier on input' : not supported in this stage: fragment
-ERROR: 1 compilation errors.  No code generated.
+ERROR: 0:18: 'location' : repeated use of location 41
+ERROR: 0:19: 'location' : repeated use of location 40
+ERROR: 3 compilation errors.  No code generated.
 
 
 ERROR: node is still EOpNull!
@@ -25,6 +27,9 @@ ERROR: node is still EOpNull!
 0:?     'c' (layout(location=1 ) out mediump 4-component vector of float)
 0:?     'p' (layout(location=3 ) out mediump 4-component vector of float)
 0:?     'q' (layout(location=4 ) out 2-element array of mediump 4-component vector of float)
+0:?     'ca' (layout(location=40 ) out 4-element array of mediump float)
+0:?     'cb' (layout(location=41 ) out 2-element array of mediump float)
+0:?     'cc' (layout(location=39 ) out 6-element array of mediump float)
 
 
 Linked fragment stage:
diff --git a/Test/baseResults/300layout.vert.out b/Test/baseResults/300layout.vert.out
index d303b5db..ae183bfc 100644
--- a/Test/baseResults/300layout.vert.out
+++ b/Test/baseResults/300layout.vert.out
@@ -2,6 +2,7 @@
 ERROR: 0:7: 'vertex input arrays' : not supported with this profile: es
 ERROR: 0:8: 'in' : cannot be a structure or array 
 ERROR: 0:8: 'vertex input arrays' : not supported with this profile: es
+ERROR: 0:8: 'location' : repeated use of location 10
 ERROR: 0:12: 'badm4' : cannot specify matrix layout on a variable declaration 
 ERROR: 0:12: 'badm4' : cannot specify packing on a variable declaration 
 ERROR: 0:19: 'badf' : member of uniform block cannot have an auxiliary or interpolation qualifier 
@@ -15,7 +16,8 @@ ERROR: 0:42: 'location qualifier on output' : not supported in this stage: verte
 ERROR: 0:50: 'shared' : not supported with this profile: es
 ERROR: 0:50: 'shared' : not supported in this stage: vertex
 ERROR: 0:54: 'aoeuntaoeu' : layout qualifiers for matrix layout and packing only apply to uniform or buffer blocks 
-ERROR: 16 compilation errors.  No code generated.
+ERROR: 0:57: 'location' : repeated use of location 40
+ERROR: 18 compilation errors.  No code generated.
 
 
 ERROR: node is still EOpNull!
@@ -72,6 +74,8 @@ ERROR: node is still EOpNull!
 0:?     'badoutA' (layout(location=10 ) smooth out highp 4-component vector of float)
 0:?     'compute_only' (shared highp 4-component vector of float)
 0:?     'aoeuntaoeu' (layout(packed ) highp float)
+0:?     'cd' (layout(location=40 ) in highp float)
+0:?     'ce' (layout(location=37 ) in highp 4X3 matrix of float)
 0:?     'gl_VertexID' (gl_VertexId highp int)
 0:?     'gl_InstanceID' (gl_InstanceId highp int)
 
diff --git a/Test/baseResults/400.frag.out b/Test/baseResults/400.frag.out
index e6e33689..936cf2b2 100644
--- a/Test/baseResults/400.frag.out
+++ b/Test/baseResults/400.frag.out
@@ -197,7 +197,7 @@ ERROR: node is still EOpNull!
 0:?     'isamp2DA' (uniform isampler2DArray)
 0:?     'gl_ClipDistance' (smooth in 4-element array of float)
 0:?     'vl' (layout(location=4 ) smooth in 4-component vector of float)
-0:?     'vl2' (layout(location=4 ) smooth in 4-component vector of float)
+0:?     'vl2' (layout(location=6 ) smooth in 4-component vector of float)
 0:?     'uv3' (layout(location=3 ) uniform 3-component vector of float)
 0:?     '__anon__0' (in block{gl_FogFragCoord,gl_TexCoord,gl_Color,gl_SecondaryColor})
 0:?     '__anon__0' (in block{gl_FogFragCoord,gl_TexCoord,gl_Color,gl_SecondaryColor})
diff --git a/Test/baseResults/430.vert.out b/Test/baseResults/430.vert.out
index 54d80601..5b7a5aa2 100644
--- a/Test/baseResults/430.vert.out
+++ b/Test/baseResults/430.vert.out
@@ -11,7 +11,8 @@ ERROR: 0:25: 'm3' : cannot use layout qualifiers on structure members
 ERROR: 0:28: '' : cannot use invariant qualifier on a function parameter 
 ERROR: 0:30: '' : cannot use layout qualifiers on a function parameter 
 ERROR: 0:31: '' : cannot use auxiliary or interpolation qualifiers on a function parameter 
-ERROR: 11 compilation errors.  No code generated.
+ERROR: 0:42: 'location' : repeated use of location 53
+ERROR: 12 compilation errors.  No code generated.
 
 
 ERROR: node is still EOpNull!
@@ -36,10 +37,13 @@ ERROR: node is still EOpNull!
 0:31      'cv3' (in 3-component vector of float)
 0:?   Linker Objects
 0:?     'v4' (layout(location=3 ) 4-component vector of float)
-0:?     'uv4' (layout(location=3 ) uniform 4-component vector of float)
+0:?     'uv4' (layout(location=4 ) uniform 4-component vector of float)
 0:?     'b1' (layout(location=2 ) in block{v})
 0:?     'b2' (layout(location=2 ) out block{v})
 0:?     '__anon__0' (out block{gl_ClipDistance})
+0:?     'cs' (layout(location=10 ) smooth out 2-element array of structure{m,f})
+0:?     'cf' (layout(location=54 ) smooth out float)
+0:?     'cg' (layout(location=53 ) smooth out float)
 0:?     'gl_VertexID' (gl_VertexId int)
 0:?     'gl_InstanceID' (gl_InstanceId int)
 
diff --git a/Test/baseResults/specExamples.frag.out b/Test/baseResults/specExamples.frag.out
index 4668014b..2629e783 100644
--- a/Test/baseResults/specExamples.frag.out
+++ b/Test/baseResults/specExamples.frag.out
@@ -16,6 +16,7 @@ ERROR: 0:99: 'local_size_y' : there is no such layout identifier for this stage
 ERROR: 0:100: 'local_size_x' : there is no such layout identifier for this stage taking an assigned value 
 ERROR: 0:102: 'color' : redefinition 
 ERROR: 0:103: 'index' : there is no such layout identifier for this stage taking an assigned value 
+ERROR: 0:104: 'location' : repeated use of location 3
 ERROR: 0:106: 'depth_greater' : unrecognized layout identifier, or qualifier requires assignemnt (e.g., binding = 4) 
 ERROR: 0:112: 'depth_any' : unrecognized layout identifier, or qualifier requires assignemnt (e.g., binding = 4) 
 ERROR: 0:115: 'depth_greater' : unrecognized layout identifier, or qualifier requires assignemnt (e.g., binding = 4) 
@@ -48,7 +49,7 @@ ERROR: 0:226: 'in' : not allowed in nested scope
 ERROR: 0:227: 'in' : not allowed in nested scope 
 ERROR: 0:228: 'in' : not allowed in nested scope 
 ERROR: 0:232: 'out' : not allowed in nested scope 
-ERROR: 48 compilation errors.  No code generated.
+ERROR: 49 compilation errors.  No code generated.
 
 
 gl_FragCoord pixel center is integer
diff --git a/glslang/Include/revision.h b/glslang/Include/revision.h
index 1c7db6ba..9efa61a7 100644
--- a/glslang/Include/revision.h
+++ b/glslang/Include/revision.h
@@ -9,5 +9,5 @@
 // source have to figure out how to create revision.h just to get a build
 // going.  However, if it is not updated, it can be a version behind.
 
-#define GLSLANG_REVISION "24355"
-#define GLSLANG_DATE     "2013/12/04 14:48:20"
+#define GLSLANG_REVISION "24356"
+#define GLSLANG_DATE     "2013/12/04 14:50:38"
diff --git a/glslang/MachineIndependent/ParseHelper.cpp b/glslang/MachineIndependent/ParseHelper.cpp
index c3febee0..9d80e3ea 100644
--- a/glslang/MachineIndependent/ParseHelper.cpp
+++ b/glslang/MachineIndependent/ParseHelper.cpp
@@ -2649,6 +2649,10 @@ void TParseContext::layoutTypeCheck(TSourceLoc loc, const TSymbol& symbol)
         default:
             break;
         }
+
+        int repeated = intermediate.addUsedLocation(qualifier, type);
+        if (repeated >= 0)
+            error(loc, "repeated use of location", "location", "%d", repeated);
     }
 
     if (qualifier.hasBinding()) {
diff --git a/glslang/MachineIndependent/linkValidate.cpp b/glslang/MachineIndependent/linkValidate.cpp
index b0669128..bacf4449 100644
--- a/glslang/MachineIndependent/linkValidate.cpp
+++ b/glslang/MachineIndependent/linkValidate.cpp
@@ -443,4 +443,95 @@ bool TIntermediate::userOutputUsed() const
     return found;
 }
 
+// Accumulate locations used for inputs, outputs, and uniforms, and check for collisions
+// as the accumulation is done.
+//
+// Returns < 0 if no collision, >= 0 if collision and the value returned is a colliding value.
+int TIntermediate::addUsedLocation(const TQualifier& qualifier, const TType& type)
+{
+    int set;
+    if (qualifier.isPipeInput())
+        set = 0;
+    else if (qualifier.isPipeOutput())
+        set = 1;
+    else if (qualifier.isUniform())
+        set = 2;
+    else
+        return -1;
+
+    int size;
+    if (qualifier.isUniform()) {
+        if (type.isArray())
+            size = type.getArraySize();
+        else
+            size = 1;
+    } else
+        size = computeTypeLocationSize(type);
+
+    TRange range = { qualifier.layoutSlotLocation, qualifier.layoutSlotLocation + size - 1 };
+
+    // check for collisions
+    for (size_t r = 0; r < usedLocations[set].size(); ++r) {
+        if (range.last  >= usedLocations[set][r].start &&
+            range.start <= usedLocations[set][r].last) {
+            // there is a collision; pick one
+            return std::max(range.start, usedLocations[set][r].start);
+        }
+    }
+
+    usedLocations[set].push_back(range);
+
+    return -1;
+}
+
+// Recursively figure out how many locations are used up by an input or output type.
+// Return the size of type, as measured by "locations".
+int TIntermediate::computeTypeLocationSize(const TType& type)
+{
+    // "If the declared input is an array of size n and each element takes m locations, it will be assigned m * n 
+    // consecutive locations..."
+    if (type.isArray()) {
+        TType elementType(type, 0);
+        return type.getArraySize() * computeTypeLocationSize(elementType);
+    }
+
+    // "The locations consumed by block and structure members are determined by applying the rules above 
+    // recursively..."    
+    if (type.isStruct()) {
+        // TODO: 440 functionality: input/output block locations when members also have locations
+        int size = 0;
+        for (size_t member = 0; member < type.getStruct()->size(); ++member) {
+            TType memberType(type, member);
+            size += computeTypeLocationSize(memberType);
+        }
+        return size;
+    }
+
+    // "If a vertex shader input is any scalar or vector type, it will consume a single location. If a non-vertex 
+    // shader input is a scalar or vector type other than dvec3 or dvec4, it will consume a single location, while 
+    // types dvec3 or dvec4 will consume two consecutive locations. Inputs of type double and dvec2 will 
+    // consume only a single location, in all stages."
+    if (type.isScalar())
+        return 1;
+    if (type.isVector()) {
+        if (language == EShLangVertex && type.getQualifier().isPipeInput())
+            return 1;
+        if (type.getBasicType() == EbtDouble && type.getVectorSize() > 2)
+            return 2;
+        else
+            return 1;
+    }
+
+    // "If the declared input is an n x m single- or double-precision matrix, ...
+    // The number of locations assigned for each matrix will be the same as 
+    // for an n-element array of m-component vectors..."
+    if (type.isMatrix()) {
+        TType columnType(type, 0);
+        return type.getMatrixCols() * computeTypeLocationSize(columnType);
+    }
+
+    assert(0);
+    return 1;
+}
+
 } // end namespace glslang
diff --git a/glslang/MachineIndependent/localintermediate.h b/glslang/MachineIndependent/localintermediate.h
index 5eb9d8bc..52a4aa66 100644
--- a/glslang/MachineIndependent/localintermediate.h
+++ b/glslang/MachineIndependent/localintermediate.h
@@ -155,6 +155,8 @@ public:
     void addIoAccessed(const TString& name) { ioAccessed.insert(name); }
     bool inIoAccessed(const TString& name) const { return ioAccessed.find(name) != ioAccessed.end(); }
 
+    int addUsedLocation(const TQualifier&, const TType&);
+
 protected:
     void error(TInfoSink& infoSink, const char*);
     void mergeBodies(TInfoSink&, TIntermSequence& globals, const TIntermSequence& unitGlobals);
@@ -164,6 +166,7 @@ protected:
     void inOutLocationCheck(TInfoSink&);
     TIntermSequence& findLinkerObjects() const;
     bool userOutputUsed() const;
+    int computeTypeLocationSize(const TType&);
 
 protected:
     const EShLanguage language;
@@ -194,6 +197,12 @@ protected:
 
     std::set<TString> ioAccessed;  // set of names of statically read/written I/O that might need extra checking
 
+    struct TRange {
+        int start;
+        int last;
+    };
+    std::vector<TRange> usedLocations[3];    // sets of used locations, one for each of in, out, and uniform
+
 private:
     void operator=(TIntermediate&); // prevent assignments
 };