Describe disabling preallocated symbols in the doc.

2 files changed, 14 insertions, 0 deletions

diff --git a/doc/guides/compile.md b/doc/guides/compile.md
index 3a6551f53..a8e35b65c 100644
--- a/doc/guides/compile.md
+++ b/doc/guides/compile.md
@@ -226,6 +226,15 @@ conf.exts do |exts|
 end
 ```
 
+### Preallocated Symbols
+
+By far, preallocate symbols are highly compatible with the previous versions, so
+we expect you won't see any problem with them. But just in case you face any
+issue, you can disable preallocated symbols by specifying `conf.disable_presym`.
+
+In the build process, `mrbc` under cross compiling environment will be compiled
+with this configuration.
+
 ### Mrbgems
 
 `mruby` comes with the (sort of) packaging system named `mrbgems`. To
diff --git a/doc/guides/symbol.md b/doc/guides/symbol.md
index 6943b2e26..9236a3c0d 100644
--- a/doc/guides/symbol.md
+++ b/doc/guides/symbol.md
@@ -76,3 +76,8 @@ these macros are expanded to `mrb_intern_lit` calls, therefore the mruby state
 variable is required. The above macros assume the variable name is `mrb`.  If
 its name is not `mrb`, you need to use macros with `_2` suffix, such as
 `MRB_SYM_2` to specify `mrb_state*` variable.
+
+### Disabling Preallocated Symbols
+
+By defining `MRB_NO_PRESYM` macro, you can disable preallocated symbols.
+Or you can specify `conf.disable_presym` in the configuration file.