Add zero-value check when parsing `f' line. Fixes #140.

models/issue-140-zero-face-idx.mtl

@@ -0,0 +1,2 @@
+newmtl main
+Kd 1 1 1

models/issue-140-zero-face-idx.obj

@@ -0,0 +1,17 @@
+mtllib issue-140-zero-face-idx.mtl
+
+v -0.5 -0.5 0
+v 0.5 -0.5 0
+v 0.5 0.5 0
+v -0.5 0.5 0
+
+vt 0 0 0
+vt 1 0 0
+vt 1 1 0
+vt 0 1 0
+
+vn 0 0 -1
+
+usemtl main
+f 0/0/0 1/1/0 3/3/0
+f 1/1/0 3/3/0 2/2/0

tests/tester.cc

@@ -643,6 +643,23 @@ TEST_CASE("norm_texopts", "[norm]") {
 
 }
 
+TEST_CASE("zero-face-idx-value", "[Issue140]") {
+  tinyobj::attrib_t attrib;
+  std::vector<tinyobj::shape_t> shapes;
+  std::vector<tinyobj::material_t> materials;
+
+  std::string err;
+  bool ret = tinyobj::LoadObj(&attrib, &shapes, &materials, &err, "../models/issue-140-zero-face-idx.obj", gMtlBasePath);
+
+  
+  if (!err.empty()) {
+    std::cerr << err << std::endl;
+  }
+  REQUIRE(false == ret);
+  REQUIRE(!err.empty());
+
+}
+
 #if 0
 int
 main(

tiny_obj_loader.h

@@ -364,7 +364,6 @@ namespace tinyobj {
 
 MaterialReader::~MaterialReader() {}
 
-
 struct vertex_index {
   int v_idx, vt_idx, vn_idx;
   vertex_index() : v_idx(-1), vt_idx(-1), vn_idx(-1) {}
@@ -428,10 +427,27 @@ static std::istream &safeGetline(std::istream &is, std::string &t) {
 #define IS_NEW_LINE(x) (((x) == '\r') || ((x) == '\n') || ((x) == '\0'))
 
 // Make index zero-base, and also support relative index.
-static inline int fixIndex(int idx, int n) {
-  if (idx > 0) return idx - 1;
-  if (idx == 0) return 0;
-  return n + idx;  // negative value = relative
+static inline bool fixIndex(int idx, int n, int *ret) {
+  if (!ret) {
+    return false;
+  }
+
+  if (idx > 0) {
+    (*ret) = idx - 1;
+    return true;
+  }
+
+  if (idx == 0) {
+    // zero is not allowed according to the spec.
+    return false;
+  }
+
+  if (idx < 0) {
+    (*ret) = n + idx;  // negative value = relative
+    return true;
+  }
+
+  return false;  // never reach here.
 }
 
 static inline std::string parseString(const char **token) {
@@ -584,9 +600,9 @@ static bool tryParseDouble(const char *s, const char *s_end, double *result) {
   }
 
 assemble:
-  *result =
-      (sign == '+' ? 1 : -1) *
-      (exponent ? std::ldexp(mantissa * std::pow(5.0, exponent), exponent) : mantissa);
+  *result = (sign == '+' ? 1 : -1) *
+            (exponent ? std::ldexp(mantissa * std::pow(5.0, exponent), exponent)
+                      : mantissa);
   return true;
 fail:
   return false;
@@ -609,8 +625,8 @@ static inline void parseReal2(real_t *x, real_t *y, const char **token,
   (*y) = parseReal(token, default_y);
 }
 
-static inline void parseReal3(real_t *x, real_t *y, real_t *z, const char **token,
-                               const double default_x = 0.0,
+static inline void parseReal3(real_t *x, real_t *y, real_t *z,
+                              const char **token, const double default_x = 0.0,
                               const double default_y = 0.0,
                               const double default_z = 0.0) {
   (*x) = parseReal(token, default_x);
@@ -694,37 +710,57 @@ static tag_sizes parseTagTriple(const char **token) {
 }
 
 // Parse triples with index offsets: i, i/j/k, i//k, i/j
-static vertex_index parseTriple(const char **token, int vsize, int vnsize,
-                                int vtsize) {
+static bool parseTriple(const char **token, int vsize, int vnsize, int vtsize,
+                        vertex_index *ret) {
+  if (!ret) {
+    return false;
+  }
+
   vertex_index vi(-1);
 
-  vi.v_idx = fixIndex(atoi((*token)), vsize);
+  if (!fixIndex(atoi((*token)), vsize, &(vi.v_idx))) {
+    return false;
+  }
+
   (*token) += strcspn((*token), "/ \t\r");
   if ((*token)[0] != '/') {
-    return vi;
+    (*ret) = vi;
+    return true;
   }
   (*token)++;
 
   // i//k
   if ((*token)[0] == '/') {
     (*token)++;
-    vi.vn_idx = fixIndex(atoi((*token)), vnsize);
+    if (!fixIndex(atoi((*token)), vnsize, &(vi.vn_idx))) {
+      return false;
+    }
     (*token) += strcspn((*token), "/ \t\r");
-    return vi;
+    (*ret) = vi;
+    return true;
   }
 
   // i/j/k or i/j
-  vi.vt_idx = fixIndex(atoi((*token)), vtsize);
+  if (!fixIndex(atoi((*token)), vtsize, &(vi.vt_idx))) {
+    return false;
+  }
+
   (*token) += strcspn((*token), "/ \t\r");
   if ((*token)[0] != '/') {
-    return vi;
+    (*ret) = vi;
+    return true;
   }
 
   // i/j/k
   (*token)++;  // skip '/'
-  vi.vn_idx = fixIndex(atoi((*token)), vnsize);
+  if (!fixIndex(atoi((*token)), vnsize, &(vi.vn_idx))) {
+    return false;
+  }
   (*token) += strcspn((*token), "/ \t\r");
-  return vi;
+
+  (*ret) = vi;
+
+  return true;
 }
 
 // Parse raw triples: i, i/j/k, i//k, i/j
@@ -1532,9 +1568,16 @@ bool LoadObj(attrib_t *attrib, std::vector<shape_t> *shapes,
       face.reserve(3);
 
       while (!IS_NEW_LINE(token[0])) {
-        vertex_index vi = parseTriple(&token, static_cast<int>(v.size() / 3),
+        vertex_index vi;
+        if (!parseTriple(&token, static_cast<int>(v.size() / 3),
                          static_cast<int>(vn.size() / 3),
-                                      static_cast<int>(vt.size() / 2));
+                         static_cast<int>(vt.size() / 2), &vi)) {
+          if (err) {
+            (*err) = "Failed parse `f' line(e.g. zero value for face index).\n";
+          }
+          return false;
+        }
+
         face.push_back(vi);
         size_t n = strspn(token, " \t\r");
         token += n;