Patchwork Using array_length macro outside function

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Submitter TAMUKI Shoichi
Date Feb. 4, 2019, 5:53 a.m.
Message ID <201902040553.AA04223@tamuki.linet.gr.jp>
Download mbox | patch
Permalink /patch/31290/
State New
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TAMUKI Shoichi - Feb. 4, 2019, 5:53 a.m.
Hello,

As for time/tst-strftime2.c, I implemented using array_length macro
[1] to calculate the number of elements in the array.

[1] https://sourceware.org/ml/libc-alpha/2017-10/msg01054.html

Now, I tried to further improve this as patched below;

----------------------------------------------------------------------
----------------------------------------------------------------------

Can we remove the type validation from the current array_length macro?

Or is there any way to use array_length macro outside function keeping
the type validation?

It seems that elf/dl-load.c has the same situation:

----------------------------------------------------------------------
static const size_t system_dirs_len[] =
{
  SYSTEM_DIRS_LEN
};
#define nsystem_dirs_len array_length (system_dirs_len)
----------------------------------------------------------------------

Thoughts?

Regards,
TAMUKI Shoichi

Patch

diff --git a/time/tst-strftime2.c b/time/tst-strftime2.c
index 57d2144..6c2d359 100644
--- a/time/tst-strftime2.c
+++ b/time/tst-strftime2.c
@@ -25,8 +25,10 @@ 
 #include <string.h>
 
 static const char *locales[] = { "ja_JP.UTF-8", "lo_LA.UTF-8", "th_TH.UTF-8" };
+#define nlocales array_length (locales)
 
 static const char *formats[] = { "%EY", "%_EY", "%-EY" };
+#define nformats array_length (formats)
 
 static const struct
 {
@@ -40,8 +42,9 @@  static const struct
     { 1, 3, 97 },
     { 1, 3, 98 }
   };
+#define ndates array_length (dates)
 
-static char ref[3][3][6][100];
+static char ref[nlocales][nformats][ndates][100];
 
 static void
 mkreftable (void)
@@ -51,9 +54,9 @@  mkreftable (void)
   static const int yrj[] = { 63, 64, 1, 2, 9, 10 };
   static const int yrb[] = { 2531, 2532, 2532, 2533, 2540, 2541 };
 
-  for (i = 0; i < array_length (locales); i++)
-    for (j = 0; j < array_length (formats); j++)
-      for (k = 0; k < array_length (dates); k++)
+  for (i = 0; i < nlocales; i++)
+    for (j = 0; j < nformats; j++)
+      for (k = 0; k < ndates; k++)
 	{
 	  if (i == 0)
 	    {
@@ -93,7 +96,7 @@  do_test (void)
   size_t r, e;
 
   mkreftable ();
-  for (i = 0; i < array_length (locales); i++)
+  for (i = 0; i < nlocales; i++)
     {
       if (setlocale (LC_ALL, locales[i]) == NULL)
 	{
@@ -101,9 +104,9 @@  do_test (void)
 	  continue;
 	}
       printf ("[%s]\n", locales[i]);
-      for (j = 0; j < array_length (formats); j++)
+      for (j = 0; j < nformats; j++)
 	{
-	  for (k = 0; k < array_length (dates); k++)
+	  for (k = 0; k < ndates; k++)
 	    {
 	      ttm.tm_mday = dates[k].d;
 	      ttm.tm_mon  = dates[k].m;
----------------------------------------------------------------------

and it resulted in an error and the compilation failed:

----------------------------------------------------------------------
gcc tst-strftime2.c -c -std=gnu11 -fgnu89-inline  -O2 -g -m64 -fmessage-length=0 -D_FORTIFY_SOURCE=2 -funwind-tables \
-fasynchronous-unwind-tables -U_FORTIFY_SOURCE -g -Wall -Wwrite-strings -Wundef -Werror -fmerge-all-constants -frounding-math \
-fstack-protector -Wstrict-prototypes -Wold-style-definition -fmath-errno            -I../include \
-I/home/tamuki/rpmbuild/BUILD/glibc-2.29/cc-base/time  -I/home/tamuki/rpmbuild/BUILD/glibc-2.29/cc-base  \
-I../sysdeps/unix/sysv/linux/x86_64/64  -I../sysdeps/unix/sysv/linux/x86_64  -I../sysdeps/unix/sysv/linux/x86/include \
-I../sysdeps/unix/sysv/linux/x86  -I../sysdeps/x86/nptl  -I../sysdeps/unix/sysv/linux/wordsize-64  -I../sysdeps/x86_64/nptl  \
-I../sysdeps/unix/sysv/linux/include -I../sysdeps/unix/sysv/linux  -I../sysdeps/nptl  -I../sysdeps/pthread  -I../sysdeps/gnu  \
-I../sysdeps/unix/inet  -I../sysdeps/unix/sysv  -I../sysdeps/unix/x86_64  -I../sysdeps/unix  -I../sysdeps/posix  \
-I../sysdeps/x86_64/64  -I../sysdeps/x86_64/fpu/multiarch  -I../sysdeps/x86_64/fpu  -I../sysdeps/x86/fpu/include \
-I../sysdeps/x86/fpu  -I../sysdeps/x86_64/multiarch  -I../sysdeps/x86_64  -I../sysdeps/x86  -I../sysdeps/ieee754/float128  \
-I../sysdeps/ieee754/ldbl-96/include -I../sysdeps/ieee754/ldbl-96  -I../sysdeps/ieee754/dbl-64/wordsize-64  \
-I../sysdeps/ieee754/dbl-64  -I../sysdeps/ieee754/flt-32  -I../sysdeps/wordsize-64  -I../sysdeps/ieee754  \
-I../sysdeps/generic  -I.. -I../libio -I.   -D_LIBC_REENTRANT \
-include /home/tamuki/rpmbuild/BUILD/glibc-2.29/cc-base/libc-modules.h -DMODULE_NAME=testsuite \
-include ../include/libc-symbols.h  -DPIC     -DTOP_NAMESPACE=glibc \
-o /home/tamuki/rpmbuild/BUILD/glibc-2.29/cc-base/time/tst-strftime2.o -MD -MP -MF \
/home/tamuki/rpmbuild/BUILD/glibc-2.29/cc-base/time/tst-strftime2.o.dt -MT \
/home/tamuki/rpmbuild/BUILD/glibc-2.29/cc-base/time/tst-strftime2.o
In file included from tst-strftime2.c:21:0:
../include/array_length.h:25:17: error: braced-group within expression allowed only inside a function
   __extension__ ({                                                      \
                 ^
tst-strftime2.c:28:18: note: in expansion of macro 'array_length'
 #define nlocales array_length (locales)
                  ^~~~~~~~~~~~
tst-strftime2.c:47:17: note: in expansion of macro 'nlocales'
 static char ref[nlocales][nformats][ndates][100];
                 ^~~~~~~~
../include/array_length.h:25:17: error: braced-group within expression allowed only inside a function
   __extension__ ({                                                      \
                 ^
tst-strftime2.c:31:18: note: in expansion of macro 'array_length'
 #define nformats array_length (formats)
                  ^~~~~~~~~~~~
tst-strftime2.c:47:27: note: in expansion of macro 'nformats'
 static char ref[nlocales][nformats][ndates][100];
                           ^~~~~~~~
../include/array_length.h:25:17: error: braced-group within expression allowed only inside a function
   __extension__ ({                                                      \
                 ^
tst-strftime2.c:45:16: note: in expansion of macro 'array_length'
 #define ndates array_length (dates)
                ^~~~~~~~~~~~
tst-strftime2.c:47:37: note: in expansion of macro 'ndates'
 static char ref[nlocales][nformats][ndates][100];
                                     ^~~~~~
tst-strftime2.c:47:13: error: 'ref' defined but not used [-Werror=unused-variable]
 static char ref[nlocales][nformats][ndates][100];
             ^~~
cc1: all warnings being treated as errors
make[2]: *** [../o-iterator.mk:9: /home/tamuki/rpmbuild/BUILD/glibc-2.29/cc-base/time/tst-strftime2.o] Error 1
----------------------------------------------------------------------

Can we use array_length macro outside function?

If the type validation is removed from the current array_length macro
as patched below, it can be compiled successfully.

----------------------------------------------------------------------
diff --git a/include/array_length.h b/include/array_length.h
index 65f5830..c9ce702 100644
--- a/include/array_length.h
+++ b/include/array_length.h
@@ -21,13 +21,7 @@ 
 
 /* array_length (VAR) is the number of elements in the array VAR.  VAR
    must evaluate to an array, not a pointer.  */
-#define array_length(var)                                               \
-  __extension__ ({                                                      \
-    _Static_assert (!__builtin_types_compatible_p                       \
-                    (__typeof (var), __typeof (&(var)[0])),             \
-                    "argument must be an array");                       \
-    sizeof (var) / sizeof ((var)[0]);                                   \
-  })
+#define array_length(var) (sizeof (var) / sizeof ((var)[0]))
 
 /* array_end (VAR) is a pointer one past the end of the array VAR.
    VAR must evaluate to an array, not a pointer.  */