Small improvements in the manual

doc/manual.org

@@ -617,9 +617,9 @@ when you need to run a script to figure out some compilation flags.
 =<filename>= is expected to contain a single S-expression and cannot
 contain =(:include ...)= forms.
 
-Most fields using the ordered set language also support [[Variables expansion][variables
-expansion]]. Variables are expanded after the set language is
-interpreted.
+Most fields using the ordered set language also support [[Variables
+expansion][variables expansion]].
+Variables are expanded after the set language is interpreted.
 
 ***** Variables expansion
 
@@ -651,7 +651,7 @@ In addition, =(action ...)= fields support the following special variables:
 - =exe:<path>= expands to =<path>=, except when cross-compiling, in
   which case it will expand to =<path>= from the host build context
 - =bin:<program>= expands to a path to =program=. If =program= is
-  provided by a jbuild in the workspace (see [[provide][provide stanzas]]), the
+  provided by a jbuild in the workspace (see [[provides][provides stanzas]]), the
   locally built binarry will be used, otherwise it will be searched in
   the =PATH= of the current build context
 - =findlib:<public-library-name>:<file>= expands to a path to file
@@ -808,6 +808,16 @@ compilation flags using the following fields:
   only
 
 For all these fields, =<flags>= is specified in the [[Ordered set language][ordered set language]].
+
+The default value for =(flags ...)= includes some =-w= options to set
+warnings. The exact set depends on whether =--dev= is passed to
+Jbuilder. As a result it is recommended to write =(flags ...)= fields
+as follow:
+
+#+begin_src
+  (flags (:standard <my options>))
+#+end_src
+
 ***** User actions
 
 =(action ...)= fields describe user actions. The argument can use one