lib/string: escape_to_c uses 3 digits in the octal form \nn to avoid misinterpretation

Signed-off-by: Jean Privat <jean@pryen.org>

diff --git a/lib/standard/string.nit b/lib/standard/string.nit
index db43964..e974d91 100644 (file)
--- a/lib/standard/string.nit
+++ b/lib/standard/string.nit
@@ -531,6 +531,14 @@ abstract class Text
        #
        #     assert "abAB12<>&".escape_to_c         == "abAB12<>&"
        #     assert "\n\"'\\".escape_to_c         == "\\n\\\"\\'\\\\"
+       #
+       # Most non-printable characters (bellow ASCII 32) are escaped to an octal form `\nnn`.
+       # Three digits are always used to avoid following digits to be interpreted as an element
+       # of the octal sequence.
+       #
+       #     assert "{0.ascii}{1.ascii}{8.ascii}{31.ascii}{32.ascii}".escape_to_c == "\\000\\001\\010\\037 "
+       #
+       # The exceptions are the common `\t` and `\n`.
        fun escape_to_c: String
        do
                var b = new FlatBuffer
@@ -541,7 +549,7 @@ abstract class Text
                        else if c == '\t' then
                                b.append("\\t")
                        else if c == '\0' then
-                               b.append("\\0")
+                               b.append("\\000")
                        else if c == '"' then
                                b.append("\\\"")
                        else if c == '\'' then
@@ -549,7 +557,17 @@ abstract class Text
                        else if c == '\\' then
                                b.append("\\\\")
                        else if c.ascii < 32 then
-                               b.append("\\{c.ascii.to_base(8, false)}")
+                               b.add('\\')
+                               var oct = c.ascii.to_base(8, false)
+                               # Force 3 octal digits since it is the
+                               # maximum allowed in the C specification
+                               if oct.length == 1 then
+                                       b.add('0')
+                                       b.add('0')
+                               else if oct.length == 2 then
+                                       b.add('0')
+                               end
+                               b.append(oct)
                        else
                                b.add(c)
                        end