Avoid dereferencing empty std::vector<>s.

* cairomm/context.cc: Check with empty() before using [0] on
  a vector. Apparently gcc allows this, but MSVC (probably correctly)
  does not. This fixes a crash on MS Windows.
  Bug #36020 (Robert Kurjata)

1 files changed, 17 insertions, 7 deletions

diff --git a/cairomm/context.cc b/cairomm/context.cc
index c5d10ed..95d33e2 100644
--- a/cairomm/context.cc
+++ b/cairomm/context.cc
@@ -169,7 +169,9 @@ void Context::set_dash(std::valarray<double>& dashes, double offset)
 
 void Context::set_dash(std::vector<double>& dashes, double offset)
 {
-  cairo_set_dash(cobj(), &dashes[0], dashes.size(), offset);
+  cairo_set_dash(cobj(),
+    (dashes.empty() ? 0 : &dashes[0]),
+    dashes.size(), offset);
   check_object_status_and_throw_exception(*this);
 }
 
@@ -184,7 +186,9 @@ void Context::set_dash(const std::valarray<double>& dashes, double offset)
 
 void Context::set_dash(const std::vector<double>& dashes, double offset)
 {
-  cairo_set_dash(cobj(), &dashes[0], dashes.size(), offset);
+  cairo_set_dash(cobj(),
+    (dashes.empty() ? 0 : &dashes[0]),
+    dashes.size(), offset);
   check_object_status_and_throw_exception(*this);
 }
 
@@ -590,15 +594,19 @@ void Context::show_text_glyphs(const std::string& utf8,
                                TextClusterFlags cluster_flags)
 {
   cairo_show_text_glyphs(cobj(), utf8.c_str(), utf8.size(),
-                         &glyphs[0], glyphs.size(),
-                         &clusters[0], clusters.size(),
+                         (glyphs.empty() ? 0 : &glyphs[0]),
+                         glyphs.size(),
+                         (clusters.empty() ? 0 : &clusters[0]),
+                         clusters.size(),
                          static_cast<cairo_text_cluster_flags_t>(cluster_flags));
   check_object_status_and_throw_exception(*this);
 }
 
 void Context::show_glyphs(const std::vector<Glyph>& glyphs)
 {
-  cairo_show_glyphs(cobj(), const_cast<cairo_glyph_t*>(&glyphs[0]), glyphs.size());
+  cairo_show_glyphs(cobj(),
+    const_cast<cairo_glyph_t*>((glyphs.empty() ? 0 : &glyphs[0])),
+    glyphs.size());
   check_object_status_and_throw_exception(*this);
 }
 
@@ -637,7 +645,7 @@ void Context::get_text_extents(const std::string& utf8, TextExtents& extents) co
 void Context::get_glyph_extents(const std::vector<Glyph>& glyphs, TextExtents& extents) const
 {
   cairo_glyph_extents(const_cast<cobject*>(cobj()),
-                      const_cast<cairo_glyph_t*>(&glyphs[0]),
+                      const_cast<cairo_glyph_t*>(glyphs.empty() ? 0 : &glyphs[0]),
                       glyphs.size(), &extents);
   check_object_status_and_throw_exception(*this);
 }
@@ -650,7 +658,9 @@ void Context::text_path(const std::string& utf8)
 
 void Context::glyph_path(const std::vector<Glyph>& glyphs)
 {
-  cairo_glyph_path(cobj(), const_cast<cairo_glyph_t*>(&glyphs[0]), glyphs.size());
+  cairo_glyph_path(cobj(),
+    const_cast<cairo_glyph_t*>(glyphs.empty() ? 0 : &glyphs[0]),
+    glyphs.size());
   check_object_status_and_throw_exception(*this);
 }