Tweak rb_str_modify_expand() + read() spec to try to find out why it fails on some platforms

* Use a longer string as <= 23 characters it's embedded on CRuby and
  the value of rb_str_capacity() is implementation-specific.

3 files changed, 21 insertions, 9 deletions

diff --git a/spec/ruby/optional/capi/ext/string_spec.c b/spec/ruby/optional/capi/ext/string_spec.c
index f2245be0ef..b7bfcf8c88 100644
--- a/spec/ruby/optional/capi/ext/string_spec.c
+++ b/spec/ruby/optional/capi/ext/string_spec.c
@@ -4,6 +4,7 @@
 #include <fcntl.h>
 #include <string.h>
 #include <stdarg.h>
+#include <errno.h>
 
 #include "ruby/encoding.h"
 
@@ -388,15 +389,24 @@ VALUE string_spec_RSTRING_PTR_after_yield(VALUE self, VALUE str) {
 VALUE string_spec_RSTRING_PTR_read(VALUE self, VALUE str, VALUE path) {
   char *cpath = StringValueCStr(path);
   int fd = open(cpath, O_RDONLY);
-  rb_str_modify_expand(str, 10);
+  VALUE capacities = rb_ary_new();
+  if (fd < 0) {
+    rb_syserr_fail(errno, "open");
+  }
+
+  rb_str_modify_expand(str, 30);
+  rb_ary_push(capacities, SIZET2NUM(rb_str_capacity(str)));
   char *buffer = RSTRING_PTR(str);
-  read(fd, buffer, 10);
-  rb_str_modify_expand(str, 21);
+  read(fd, buffer, 30);
+
+  rb_str_modify_expand(str, 53);
+  rb_ary_push(capacities, SIZET2NUM(rb_str_capacity(str)));
   char *buffer2 = RSTRING_PTR(str);
-  read(fd, buffer2 + 10, 11);
-  rb_str_set_len(str, 21);
+  read(fd, buffer2 + 30, 53 - 30);
+
+  rb_str_set_len(str, 53);
   close(fd);
-  return str;
+  return capacities;
 }
 
 VALUE string_spec_StringValue(VALUE self, VALUE str) {
diff --git a/spec/ruby/optional/capi/fixtures/read.txt b/spec/ruby/optional/capi/fixtures/read.txt
index f976cfd9b9..f7065a35d0 100644
--- a/spec/ruby/optional/capi/fixtures/read.txt
+++ b/spec/ruby/optional/capi/fixtures/read.txt
@@ -1 +1 @@
-fixture file contents
+fixture file contents to test read() with RSTRING_PTR
diff --git a/spec/ruby/optional/capi/string_spec.rb b/spec/ruby/optional/capi/string_spec.rb
index 151dfefef7..c6ab1ca0fe 100644
--- a/spec/ruby/optional/capi/string_spec.rb
+++ b/spec/ruby/optional/capi/string_spec.rb
@@ -599,10 +599,12 @@ describe "C-API String function" do
       @s.RSTRING_PTR_short_memcpy(str).should == "Infinity"
     end
 
-    it "allows read to update string contents" do
+    it "allows read() to update the string contents" do
       filename = fixture(__FILE__, "read.txt")
       str = ""
-      @s.RSTRING_PTR_read(str, filename).should == "fixture file contents"
+      capacities = @s.RSTRING_PTR_read(str, filename)
+      capacities.should == [30, 53]
+      str.should == "fixture file contents to test read() with RSTRING_PTR"
     end
   end