Guard against use of undefined macros in headers

In case users apply the -Wundef flag on their own C code.
tmcgilchrist · Nov 6, 2023 · 3d76183 · 3d76183
1 parent 10f1334
commit 3d76183
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Showing 4 changed files with 16 additions and 6 deletions.
diff --git a/Changes b/Changes
@@ -564,6 +564,12 @@ Working version
    review by Vincent Laviron, KC Sivaramakrishnan and Xavier Leroy,
    report by Vesa Karvonen and Carine Morel)
 
+- #12714: check whether macros are defined before using them to ensure
+  that the headers can always be used in code which turns on -Wundef
+  (or equivalent).
+  (Antonin Décimo, review by Miod Vallat, Gabriel Scherer,
+   Xavier Leroy, and David Allsopp)
+
 OCaml 5.1.1
 -----------
 

diff --git a/runtime/caml/fiber.h b/runtime/caml/fiber.h
@@ -101,6 +101,8 @@ struct stack_info {
 #elif defined(TARGET_power)
 /* ELF ABI: 4 reserved words at bottom of C stack */
   #define Reserved_space_c_stack_link 4 * 8
+#else
+  #define Reserved_space_c_stack_link 0
 #endif
 
 /* This structure is used for storing the OCaml return pointer when

diff --git a/runtime/caml/misc.h b/runtime/caml/misc.h
@@ -42,8 +42,9 @@
   #define CAMLdeprecated_typedef(name, type) typedef type name
 #endif
 
-#if defined(__GNUC__) && __STDC_VERSION__ >= 199901L \
- || defined(_MSC_VER) && _MSC_VER >= 1925
+#if defined(__GNUC__)                                           \
+    && defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L \
+    || defined(_MSC_VER) && _MSC_VER >= 1925
 
 #define CAML_STRINGIFY(x) #x
 #ifdef _MSC_VER
@@ -84,9 +85,10 @@ CAMLdeprecated_typedef(addr, char *);
    Note: CAMLnoreturn is a different macro defined in memory.h,
    to be used in function bodies rather than as a function attribute.
 */
-#if __STDC_VERSION__ >= 202300L || __cplusplus >= 201103L
+#if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 202300L    \
+    || defined(__cplusplus) && __cplusplus >= 201103L
   #define CAMLnoret [[noreturn]]
-#elif __STDC_VERSION__ >= 201112L
+#elif defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L
   #define CAMLnoret _Noreturn
 #elif defined(__GNUC__)
   #define CAMLnoret  __attribute__ ((noreturn))
@@ -561,7 +563,7 @@ CAMLextern int caml_snwprintf(wchar_t * buf,
 #    define CAMLno_asan __attribute__((no_sanitize("address")))
 #  endif
 #else
-#  if __SANITIZE_ADDRESS__
+#  if defined(__SANITIZE_ADDRESS__)
 #    undef CAMLno_asan
 #    define CAMLno_asan __attribute__((no_sanitize_address))
 #  endif

diff --git a/runtime/caml/tsan.h b/runtime/caml/tsan.h
@@ -34,7 +34,7 @@
 #    endif
 #  endif
 #else
-#  if __SANITIZE_THREAD__
+#  if defined(__SANITIZE_THREAD__)
 #    undef CAMLreally_no_tsan
 #    define CAMLreally_no_tsan __attribute__((no_sanitize_thread))
 #  endif