[Xen-devel] [PATCH RFC] ocaml: Fix compile with ocaml 4.06, use unsafe strings

[John Thomson <git@xxxxxxxxxxxxxxxxxxxxxxxxxxx>]

Use autoconf to test if ocaml version >= 4.02
If so, use -unsafe-string for ocamlopt and ocamlc

Bytes & safe-string were introduced in ocaml 4.02 (2015-07-27)

With ocaml 4.06, -safe-string is now default
This separates the types bytes (mutable string) and string

ocaml 4.06 throws errors in compiling:

/build/xen/src/xen-4.10.0/tools/ocaml/libs/xc
File "xenctrl.ml", line 295, characters 44-45:
Error: This expression has type bytes but an expression was expected of type 
string
File "xenctrl.ml", line 296, characters 25-26:
Error: This expression has type bytes but an expression was expected of type 
string

/build/xen/src/xen-4.10.0/tools/ocaml/libs/xb
File "xb.ml", line 88, characters 46-47:
Error: This expression has type bytes but an expression was expected of type 
string

With the safe-string changes, Unix.write and Unix.read use bytes, not string
val write : file_descr -> bytes -> int -> int -> int

File "xb.ml", line 152, characters 19-22:
Error: This expression has type string but an expression was expected of type 
bytes

String.blit
val blit : string -> int -> bytes -> int -> int -> unit

There may be other locations

Signed-off-by: John Thomson <git@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
---
 config/Tools.mk.in      | 1 +
 tools/configure.ac      | 7 +++++++
 tools/ocaml/common.make | 6 ++++--
 3 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/config/Tools.mk.in b/config/Tools.mk.in
index 0f79f4e0c2..d4f5bb5d38 100644
--- a/config/Tools.mk.in
+++ b/config/Tools.mk.in
@@ -50,6 +50,7 @@ GIT_HTTP            := @githttp@
 # Optional components
 XENSTAT_XENTOP      := @monitors@
 OCAML_TOOLS         := @ocamltools@
+OCAML_UNSAFE_STRING := @ocaml_unsafe_string@
 FLASK_POLICY        := @xsmpolicy@
 CONFIG_OVMF         := @ovmf@
 CONFIG_ROMBIOS      := @rombios@
diff --git a/tools/configure.ac b/tools/configure.ac
index d1a3a78d87..30964e4a41 100644
--- a/tools/configure.ac
+++ b/tools/configure.ac
@@ -299,6 +299,13 @@ AS_IF([test "x$ocamltools" = "xy"], [
                 AC_MSG_ERROR([Your version of OCaml: $OCAMLVERSION is not 
supported])])
             ocamltools="n"
         ])
+        AX_COMPARE_VERSION([$OCAMLVERSION], [ge], [4.02.0], [
+            ocaml_unsafe_string="-unsafe-string"
+            AC_SUBST(ocaml_unsafe_string)
+            AC_MSG_WARN([Your version of OCaml: $OCAMLVERSION requires 
compiling xen libraries with -unsafe-string])
+        ], [
+            ocaml_unsafe_string=""
+        ])
     ])
 ])
 
diff --git a/tools/ocaml/common.make b/tools/ocaml/common.make
index d5478f626f..d7fb80e728 100644
--- a/tools/ocaml/common.make
+++ b/tools/ocaml/common.make
@@ -11,9 +11,11 @@ OCAMLFIND ?= ocamlfind
 
 CFLAGS += -fPIC -Werror -I$(shell ocamlc -where)
 
+OCAML_UNSAFE_STRING ?=
+
 OCAMLOPTFLAG_G := $(shell $(OCAMLOPT) -h 2>&1 | sed -n 's/^  *\(-g\) .*/\1/p')
-OCAMLOPTFLAGS = $(OCAMLOPTFLAG_G) -ccopt "$(LDFLAGS)" -dtypes $(OCAMLINCLUDE) 
-cc $(CC) -w F -warn-error F
-OCAMLCFLAGS += -g $(OCAMLINCLUDE) -w F -warn-error F
+OCAMLOPTFLAGS = $(OCAMLOPTFLAG_G) -ccopt "$(LDFLAGS)" -dtypes $(OCAMLINCLUDE) 
-cc $(CC) -w F -warn-error F $(OCAML_UNSAFE_STRING)
+OCAMLCFLAGS += -g $(OCAMLINCLUDE) -w F -warn-error F $(OCAML_UNSAFE_STRING)
 
 VERSION := 4.1
 
-- 
2.16.0


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