Redefine _IO_iconv_t to store a single gconv step pointer [BZ #25097]

libio can only deal with gconv conversions which consist of a single
step.  Not using __gconv_info simplifies the data structures somewhat.

This eliminates a new GCC 10 warning about subscribing an inner
zero-length array.

Tested on x86_64-linux-gnu with mainline GCC.  Built with
build-many-glibcs.py, also with mainline GCC.  Due to GCC PR 92039,
there are failures left on 32-bit architectures with float128 support.

Change-Id: I8b4c489b619a53154712ff32e1b6f13bb92d4203

4 files changed, 52 insertions, 63 deletions

diff --git a/libio/fileops.c b/libio/fileops.c
index d84dd7c147..f81646d99c 100644
--- a/libio/fileops.c
+++ b/libio/fileops.c
@@ -331,23 +331,19 @@ _IO_new_file_fopen (FILE *fp, const char *filename, const char *mode,
 
 	  cc = fp->_codecvt = &fp->_wide_data->_codecvt;
 
-	  cc->__cd_in.__cd.__nsteps = fcts.towc_nsteps;
-	  cc->__cd_in.__cd.__steps = fcts.towc;
-
-	  cc->__cd_in.__cd.__data[0].__invocation_counter = 0;
-	  cc->__cd_in.__cd.__data[0].__internal_use = 1;
-	  cc->__cd_in.__cd.__data[0].__flags = __GCONV_IS_LAST;
-	  cc->__cd_in.__cd.__data[0].__statep = &result->_wide_data->_IO_state;
-
-	  cc->__cd_out.__cd.__nsteps = fcts.tomb_nsteps;
-	  cc->__cd_out.__cd.__steps = fcts.tomb;
-
-	  cc->__cd_out.__cd.__data[0].__invocation_counter = 0;
-	  cc->__cd_out.__cd.__data[0].__internal_use = 1;
-	  cc->__cd_out.__cd.__data[0].__flags
-	    = __GCONV_IS_LAST | __GCONV_TRANSLIT;
-	  cc->__cd_out.__cd.__data[0].__statep =
-	    &result->_wide_data->_IO_state;
+	  cc->__cd_in.step = fcts.towc;
+
+	  cc->__cd_in.step_data.__invocation_counter = 0;
+	  cc->__cd_in.step_data.__internal_use = 1;
+	  cc->__cd_in.step_data.__flags = __GCONV_IS_LAST;
+	  cc->__cd_in.step_data.__statep = &result->_wide_data->_IO_state;
+
+	  cc->__cd_out.step = fcts.tomb;
+
+	  cc->__cd_out.step_data.__invocation_counter = 0;
+	  cc->__cd_out.step_data.__internal_use = 1;
+	  cc->__cd_out.step_data.__flags = __GCONV_IS_LAST | __GCONV_TRANSLIT;
+	  cc->__cd_out.step_data.__statep = &result->_wide_data->_IO_state;
 
 	  /* From now on use the wide character callback functions.  */
 	  _IO_JUMPS_FILE_plus (fp) = fp->_wide_data->_wide_vtable;
diff --git a/libio/iofclose.c b/libio/iofclose.c
index 398b86d597..3c648d6c13 100644
--- a/libio/iofclose.c
+++ b/libio/iofclose.c
@@ -62,8 +62,8 @@ _IO_new_fclose (FILE *fp)
       struct _IO_codecvt *cc = fp->_codecvt;
 
       __libc_lock_lock (__gconv_lock);
-      __gconv_release_step (cc->__cd_in.__cd.__steps);
-      __gconv_release_step (cc->__cd_out.__cd.__steps);
+      __gconv_release_step (cc->__cd_in.step);
+      __gconv_release_step (cc->__cd_out.step);
       __libc_lock_unlock (__gconv_lock);
     }
   else
diff --git a/libio/iofwide.c b/libio/iofwide.c
index 10e2d66f6b..3acebba07d 100644
--- a/libio/iofwide.c
+++ b/libio/iofwide.c
@@ -80,22 +80,19 @@ _IO_fwide (FILE *fp, int mode)
 	assert (fcts.towc_nsteps == 1);
 	assert (fcts.tomb_nsteps == 1);
 
-	cc->__cd_in.__cd.__nsteps = fcts.towc_nsteps;
-	cc->__cd_in.__cd.__steps = fcts.towc;
-
-	cc->__cd_in.__cd.__data[0].__invocation_counter = 0;
-	cc->__cd_in.__cd.__data[0].__internal_use = 1;
-	cc->__cd_in.__cd.__data[0].__flags = __GCONV_IS_LAST;
-	cc->__cd_in.__cd.__data[0].__statep = &fp->_wide_data->_IO_state;
-
-	cc->__cd_out.__cd.__nsteps = fcts.tomb_nsteps;
-	cc->__cd_out.__cd.__steps = fcts.tomb;
-
-	cc->__cd_out.__cd.__data[0].__invocation_counter = 0;
-	cc->__cd_out.__cd.__data[0].__internal_use = 1;
-	cc->__cd_out.__cd.__data[0].__flags
-	  = __GCONV_IS_LAST | __GCONV_TRANSLIT;
-	cc->__cd_out.__cd.__data[0].__statep = &fp->_wide_data->_IO_state;
+	cc->__cd_in.step = fcts.towc;
+
+	cc->__cd_in.step_data.__invocation_counter = 0;
+	cc->__cd_in.step_data.__internal_use = 1;
+	cc->__cd_in.step_data.__flags = __GCONV_IS_LAST;
+	cc->__cd_in.step_data.__statep = &fp->_wide_data->_IO_state;
+
+	cc->__cd_out.step = fcts.tomb;
+
+	cc->__cd_out.step_data.__invocation_counter = 0;
+	cc->__cd_out.step_data.__internal_use = 1;
+	cc->__cd_out.step_data.__flags = __GCONV_IS_LAST | __GCONV_TRANSLIT;
+	cc->__cd_out.step_data.__statep = &fp->_wide_data->_IO_state;
       }
 
       /* From now on use the wide character callback functions.  */
@@ -117,14 +114,14 @@ __libio_codecvt_out (struct _IO_codecvt *codecvt, __mbstate_t *statep,
 {
   enum __codecvt_result result;
 
-  struct __gconv_step *gs = codecvt->__cd_out.__cd.__steps;
+  struct __gconv_step *gs = codecvt->__cd_out.step;
   int status;
   size_t dummy;
   const unsigned char *from_start_copy = (unsigned char *) from_start;
 
-  codecvt->__cd_out.__cd.__data[0].__outbuf = (unsigned char *) to_start;
-  codecvt->__cd_out.__cd.__data[0].__outbufend = (unsigned char *) to_end;
-  codecvt->__cd_out.__cd.__data[0].__statep = statep;
+  codecvt->__cd_out.step_data.__outbuf = (unsigned char *) to_start;
+  codecvt->__cd_out.step_data.__outbufend = (unsigned char *) to_end;
+  codecvt->__cd_out.step_data.__statep = statep;
 
   __gconv_fct fct = gs->__fct;
 #ifdef PTR_DEMANGLE
@@ -133,12 +130,12 @@ __libio_codecvt_out (struct _IO_codecvt *codecvt, __mbstate_t *statep,
 #endif
 
   status = DL_CALL_FCT (fct,
-			(gs, codecvt->__cd_out.__cd.__data, &from_start_copy,
+			(gs, &codecvt->__cd_out.step_data, &from_start_copy,
 			 (const unsigned char *) from_end, NULL,
 			 &dummy, 0, 0));
 
   *from_stop = (wchar_t *) from_start_copy;
-  *to_stop = (char *) codecvt->__cd_out.__cd.__data[0].__outbuf;
+  *to_stop = (char *) codecvt->__cd_out.step_data.__outbuf;
 
   switch (status)
     {
@@ -169,14 +166,14 @@ __libio_codecvt_in (struct _IO_codecvt *codecvt, __mbstate_t *statep,
 {
   enum __codecvt_result result;
 
-  struct __gconv_step *gs = codecvt->__cd_in.__cd.__steps;
+  struct __gconv_step *gs = codecvt->__cd_in.step;
   int status;
   size_t dummy;
   const unsigned char *from_start_copy = (unsigned char *) from_start;
 
-  codecvt->__cd_in.__cd.__data[0].__outbuf = (unsigned char *) to_start;
-  codecvt->__cd_in.__cd.__data[0].__outbufend = (unsigned char *) to_end;
-  codecvt->__cd_in.__cd.__data[0].__statep = statep;
+  codecvt->__cd_in.step_data.__outbuf = (unsigned char *) to_start;
+  codecvt->__cd_in.step_data.__outbufend = (unsigned char *) to_end;
+  codecvt->__cd_in.step_data.__statep = statep;
 
   __gconv_fct fct = gs->__fct;
 #ifdef PTR_DEMANGLE
@@ -185,12 +182,12 @@ __libio_codecvt_in (struct _IO_codecvt *codecvt, __mbstate_t *statep,
 #endif
 
   status = DL_CALL_FCT (fct,
-			(gs, codecvt->__cd_in.__cd.__data, &from_start_copy,
+			(gs, &codecvt->__cd_in.step_data, &from_start_copy,
 			 (const unsigned char *) from_end, NULL,
 			 &dummy, 0, 0));
 
   *from_stop = (const char *) from_start_copy;
-  *to_stop = (wchar_t *) codecvt->__cd_in.__cd.__data[0].__outbuf;
+  *to_stop = (wchar_t *) codecvt->__cd_in.step_data.__outbuf;
 
   switch (status)
     {
@@ -217,16 +214,16 @@ int
 __libio_codecvt_encoding (struct _IO_codecvt *codecvt)
 {
   /* See whether the encoding is stateful.  */
-  if (codecvt->__cd_in.__cd.__steps[0].__stateful)
+  if (codecvt->__cd_in.step->__stateful)
     return -1;
   /* Fortunately not.  Now determine the input bytes for the conversion
      necessary for each wide character.  */
-  if (codecvt->__cd_in.__cd.__steps[0].__min_needed_from
-      != codecvt->__cd_in.__cd.__steps[0].__max_needed_from)
+  if (codecvt->__cd_in.step->__min_needed_from
+      != codecvt->__cd_in.step->__max_needed_from)
     /* Not a constant value.  */
     return 0;
 
-  return codecvt->__cd_in.__cd.__steps[0].__min_needed_from;
+  return codecvt->__cd_in.step->__min_needed_from;
 }
 
 
@@ -238,12 +235,12 @@ __libio_codecvt_length (struct _IO_codecvt *codecvt, __mbstate_t *statep,
   int result;
   const unsigned char *cp = (const unsigned char *) from_start;
   wchar_t to_buf[max];
-  struct __gconv_step *gs = codecvt->__cd_in.__cd.__steps;
+  struct __gconv_step *gs = codecvt->__cd_in.step;
   size_t dummy;
 
-  codecvt->__cd_in.__cd.__data[0].__outbuf = (unsigned char *) to_buf;
-  codecvt->__cd_in.__cd.__data[0].__outbufend = (unsigned char *) &to_buf[max];
-  codecvt->__cd_in.__cd.__data[0].__statep = statep;
+  codecvt->__cd_in.step_data.__outbuf = (unsigned char *) to_buf;
+  codecvt->__cd_in.step_data.__outbufend = (unsigned char *) &to_buf[max];
+  codecvt->__cd_in.step_data.__statep = statep;
 
   __gconv_fct fct = gs->__fct;
 #ifdef PTR_DEMANGLE
@@ -252,7 +249,7 @@ __libio_codecvt_length (struct _IO_codecvt *codecvt, __mbstate_t *statep,
 #endif
 
   DL_CALL_FCT (fct,
-	       (gs, codecvt->__cd_in.__cd.__data, &cp,
+	       (gs, &codecvt->__cd_in.step_data, &cp,
 		(const unsigned char *) from_end, NULL,
 		&dummy, 0, 0));
 
diff --git a/libio/libio.h b/libio/libio.h
index bed324e57d..3be2fe81f6 100644
--- a/libio/libio.h
+++ b/libio/libio.h
@@ -48,14 +48,10 @@
 #include <bits/types/wint_t.h>
 #include <gconv.h>
 
-typedef union
+typedef struct
 {
-  struct __gconv_info __cd;
-  struct
-  {
-    struct __gconv_info __cd;
-    struct __gconv_step_data __data;
-  } __combined;
+  struct __gconv_step *step;
+  struct __gconv_step_data step_data;
 } _IO_iconv_t;
 
 #include <shlib-compat.h>