Fix compilation errors with CC="clang -D_FORTIFY_SOURCE=2" on Android

[Bruno Haible]

On Android, clang does not define _FORTIFY_SOURCE by default, but the Android
NDK sets CC to something like "clang -D_FORTIFY_SOURCE=2". Then, we see
compilation errors, such as

clang -ferror-limit=0 -D_FORTIFY_SOURCE=2 -DHAVE_CONFIG_H -DEXEEXT=\"\" 
-DEXEEXT=\"\" -DNO_XMALLOC -DEXEEXT=\"\" -I. -I../../gllib -I..  
-DGNULIB_STRICT_CHECKING=1 -I/data/data/com.termux/files/home/local/include 
-Wall -fvisibility=hidden -O2 -c -o strverscmp.o ../../gllib/strverscmp.c
In file included from ../../gllib/strverscmp.c:26:
In file included from ./string.h:41:
In file included from /data/data/com.termux/files/usr/include/string.h:187:
/data/data/com.termux/files/usr/include/bits/fortify/string.h:95:47: error: use 
of undeclared identifier '__USE_FORTIFY_LEVEL'
        __clang_error_if(__bos_unevaluated_le(__bos(dst), 
__builtin_strlen(src)),
                                              ^
../../gllib/cdefs.h:144:48: note: expanded from macro '__bos'
#define __bos(ptr) __builtin_object_size (ptr, __USE_FORTIFY_LEVEL > 1)
                                               ^
In file included from ../../gllib/strverscmp.c:26:
In file included from ./string.h:41:
In file included from /data/data/com.termux/files/usr/include/string.h:187:
/data/data/com.termux/files/usr/include/bits/fortify/string.h:95:47: error: use 
of undeclared identifier '__USE_FORTIFY_LEVEL'
../../gllib/cdefs.h:144:48: note: expanded from macro '__bos'
#define __bos(ptr) __builtin_object_size (ptr, __USE_FORTIFY_LEVEL > 1)
                                               ^

Find the full list of errors from a Gnulib testdir attached.


The cause is that Android has its own framework for defining fortified
variants of the string operations, and like glibc it uses macros named
'__bos' and '__bos0'. But these macros have different definitions in
Android than in glibc. Using the glibc definition on Android leads to
trouble (because it references an undefined variable __USE_FORTIFY_LEVEL).
And undefining these macros after use leads to trouble as well (namely,
link errors for the undefined function '__bos0').

So, gnulib's cdefs.h and libc-config.h needs to avoid fiddling with
the Fortify stuff when used in Gnulib. The Gnulib modules that use
libc-config, namely
  canonicalize-lgpl
  fnmatch
  glibc-internal/dynarray
  glibc-internal/scratch_buffer
  glob, glob-h
  mktime
  nstrftime
  random, random_r
  strverscmp
  tempname
are unlikely to ever use this Fortify stuff.

This patch fixes the compilation errors. The use of __GNULIB_CDEFS has a
precedent; I therefore don't expect that it will trigger resistence during
the next merge back into glibc.


2023-01-29  Bruno Haible  <bruno@clisp.org>

        Fix compilation errors with CC="clang -D_FORTIFY_SOURCE=2" on Android.
        Reported by Alexey Rochev <equeim@gmail.com> in
        
<https://lists.gnu.org/archive/html/bug-gnu-libiconv/2023-01/msg00019.html>.
        * lib/cdefs.h (__bos, __bos0, __glibc_objsize0, __glibc_objsize,
        __glibc_safe_len_cond, __glibc_unsigned_or_positive,
        __glibc_safe_or_unknown_len, __glibc_unsafe_len, __glibc_fortify,
        __glibc_fortify_n): Don't define these macros in Gnulib.
        * lib/libc-config.h: Don't undefine these macros in Gnulib.

diff --git a/lib/cdefs.h b/lib/cdefs.h
index 09a3d19b23..412f036ce3 100644
--- a/lib/cdefs.h
+++ b/lib/cdefs.h
@@ -140,32 +140,37 @@
 #endif
 
 
+/* Gnulib avoids these definitions, as they don't work on non-glibc platforms.
+   In particular, __bos and __bos0 are defined differently in the Android libc.
+ */
+#ifndef __GNULIB_CDEFS
+
 /* Fortify support.  */
-#define __bos(ptr) __builtin_object_size (ptr, __USE_FORTIFY_LEVEL > 1)
-#define __bos0(ptr) __builtin_object_size (ptr, 0)
+# define __bos(ptr) __builtin_object_size (ptr, __USE_FORTIFY_LEVEL > 1)
+# define __bos0(ptr) __builtin_object_size (ptr, 0)
 
 /* Use __builtin_dynamic_object_size at _FORTIFY_SOURCE=3 when available.  */
-#if __USE_FORTIFY_LEVEL == 3 && (__glibc_clang_prereq (9, 0)                 \
-                                || __GNUC_PREREQ (12, 0))
-# define __glibc_objsize0(__o) __builtin_dynamic_object_size (__o, 0)
-# define __glibc_objsize(__o) __builtin_dynamic_object_size (__o, 1)
-#else
-# define __glibc_objsize0(__o) __bos0 (__o)
-# define __glibc_objsize(__o) __bos (__o)
-#endif
+# if __USE_FORTIFY_LEVEL == 3 && (__glibc_clang_prereq (9, 0)                \
+                                 || __GNUC_PREREQ (12, 0))
+#  define __glibc_objsize0(__o) __builtin_dynamic_object_size (__o, 0)
+#  define __glibc_objsize(__o) __builtin_dynamic_object_size (__o, 1)
+# else
+#  define __glibc_objsize0(__o) __bos0 (__o)
+#  define __glibc_objsize(__o) __bos (__o)
+# endif
 
 /* Compile time conditions to choose between the regular, _chk and _chk_warn
    variants.  These conditions should get evaluated to constant and optimized
    away.  */
 
-#define __glibc_safe_len_cond(__l, __s, __osz) ((__l) <= (__osz) / (__s))
-#define __glibc_unsigned_or_positive(__l) \
+# define __glibc_safe_len_cond(__l, __s, __osz) ((__l) <= (__osz) / (__s))
+# define __glibc_unsigned_or_positive(__l) \
   ((__typeof (__l)) 0 < (__typeof (__l)) -1                                  \
    || (__builtin_constant_p (__l) && (__l) > 0))
 
 /* Length is known to be safe at compile time if the __L * __S <= __OBJSZ
    condition can be folded to a constant and if it is true, or unknown (-1) */
-#define __glibc_safe_or_unknown_len(__l, __s, __osz) \
+# define __glibc_safe_or_unknown_len(__l, __s, __osz) \
   ((__osz) == (__SIZE_TYPE__) -1                                             \
    || (__glibc_unsigned_or_positive (__l)                                    \
        && __builtin_constant_p (__glibc_safe_len_cond ((__SIZE_TYPE__) (__l), \
@@ -175,7 +180,7 @@
 /* Conversely, we know at compile time that the length is unsafe if the
    __L * __S <= __OBJSZ condition can be folded to a constant and if it is
    false.  */
-#define __glibc_unsafe_len(__l, __s, __osz) \
+# define __glibc_unsafe_len(__l, __s, __osz) \
   (__glibc_unsigned_or_positive (__l)                                        \
    && __builtin_constant_p (__glibc_safe_len_cond ((__SIZE_TYPE__) (__l),     \
                                                   __s, __osz))               \
@@ -184,7 +189,7 @@
 /* Fortify function f.  __f_alias, __f_chk and __f_chk_warn must be
    declared.  */
 
-#define __glibc_fortify(f, __l, __s, __osz, ...) \
+# define __glibc_fortify(f, __l, __s, __osz, ...) \
   (__glibc_safe_or_unknown_len (__l, __s, __osz)                             \
    ? __ ## f ## _alias (__VA_ARGS__)                                         \
    : (__glibc_unsafe_len (__l, __s, __osz)                                   \
@@ -194,13 +199,16 @@
 /* Fortify function f, where object size argument passed to f is the number of
    elements and not total size.  */
 
-#define __glibc_fortify_n(f, __l, __s, __osz, ...) \
+# define __glibc_fortify_n(f, __l, __s, __osz, ...) \
   (__glibc_safe_or_unknown_len (__l, __s, __osz)                             \
    ? __ ## f ## _alias (__VA_ARGS__)                                         \
    : (__glibc_unsafe_len (__l, __s, __osz)                                   \
       ? __ ## f ## _chk_warn (__VA_ARGS__, (__osz) / (__s))                  \
       : __ ## f ## _chk (__VA_ARGS__, (__osz) / (__s))))                     \
 
+#endif
+
+
 #if __GNUC_PREREQ (4,3)
 # define __warnattr(msg) __attribute__((__warning__ (msg)))
 # define __errordecl(name, msg) \
diff --git a/lib/libc-config.h b/lib/libc-config.h
index 1d28e58c97..5f5ad01037 100644
--- a/lib/libc-config.h
+++ b/lib/libc-config.h
@@ -137,8 +137,6 @@
 # undef __attribute_returns_twice__
 # undef __attribute_used__
 # undef __attribute_warn_unused_result__
-# undef __bos
-# undef __bos0
 # undef __errordecl
 # undef __extension__
 # undef __extern_always_inline
@@ -147,21 +145,13 @@
 # undef __fortified_attr_access
 # undef __fortify_function
 # undef __glibc_c99_flexarr_available
-# undef __glibc_fortify
-# undef __glibc_fortify_n
 # undef __glibc_has_attribute
 # undef __glibc_has_builtin
 # undef __glibc_has_extension
 # undef __glibc_likely
 # undef __glibc_macro_warning
 # undef __glibc_macro_warning1
-# undef __glibc_objsize
-# undef __glibc_objsize0
-# undef __glibc_safe_len_cond
-# undef __glibc_safe_or_unknown_len
 # undef __glibc_unlikely
-# undef __glibc_unsafe_len
-# undef __glibc_unsigned_or_positive
 # undef __inline
 # undef __ptr_t
 # undef __restrict
@@ -170,6 +160,18 @@
 # undef __va_arg_pack_len
 # undef __warnattr
 # undef __wur
+# ifndef __GNULIB_CDEFS
+#  undef __bos
+#  undef __bos0
+#  undef __glibc_fortify
+#  undef __glibc_fortify_n
+#  undef __glibc_objsize
+#  undef __glibc_objsize0
+#  undef __glibc_safe_len_cond
+#  undef __glibc_safe_or_unknown_len
+#  undef __glibc_unsafe_len
+#  undef __glibc_unsigned_or_positive
+# endif
 
 /* Include our copy of glibc <sys/cdefs.h>.  */
 # include <cdefs.h>

android-errors.log.gz
Description: application/gzip