string-buffer: Link to vasnprintf implementation only when needed

[Bruno Haible]

Some uses of the 'string-buffer' module don't need the *printf implementation.
In order to eliminate it from linking, when linking statically, this patch
splits up the module into two compilation units.

(The alternative would be a separate module 'string-buffer-printf', but that
leads to an excessive number of modules, IMO.)


2024-09-24  Bruno Haible  <bruno@clisp.org>

        string-buffer: Link to vasnprintf implementation only when needed.
        * lib/string-buffer-printf.c: New file, extracted from
        lib/string-buffer.c.
        * lib/string-buffer.c: Don't include <stdarg.h>.
        (sb_ensure_more_bytes): Declare. Make non-static.
        (sb_appendvf, sb_appendf): Moved to lib/string-buffer-printf.c.
        * modules/string-buffer (Files): Add lib/string-buffer-printf.c.
        (Makefile.am): Arrange to compile string-buffer-printf.c.

diff --git a/lib/string-buffer-printf.c b/lib/string-buffer-printf.c
new file mode 100644
index 0000000000..16ef4e4144
--- /dev/null
+++ b/lib/string-buffer-printf.c
@@ -0,0 +1,189 @@
+/* A buffer that accumulates a string by piecewise concatenation.
+   Copyright (C) 2021-2024 Free Software Foundation, Inc.
+
+   This file is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Lesser General Public License as
+   published by the Free Software Foundation, either version 3 of the
+   License, or (at your option) any later version.
+
+   This file is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
+
+/* Written by Bruno Haible <bruno@clisp.org>, 2021.  */
+
+#include <config.h>
+
+/* Specification.  */
+#include "string-buffer.h"
+
+/* Undocumented.  */
+extern int sb_ensure_more_bytes (struct string_buffer *buffer,
+                                 size_t increment);
+
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+int
+sb_appendvf (struct string_buffer *buffer, const char *formatstring,
+             va_list list)
+{
+  va_list list_copy;
+
+  /* Make a bit of room, so that the probability that the first vsnprintf() 
call
+     succeeds is high.  */
+  size_t room = buffer->allocated - buffer->length;
+  if (room < 64)
+    {
+      if (sb_ensure_more_bytes (buffer, 64) < 0)
+        {
+          buffer->error = true;
+          return -1;
+        }
+      room = buffer->allocated - buffer->length;
+    }
+
+  va_copy (list_copy, list);
+
+  /* First vsnprintf() call.  */
+  int ret = vsnprintf (buffer->data + buffer->length, room, formatstring, 
list);
+  if (ret < 0)
+    {
+      /* Failed.  */
+      buffer->error = true;
+      ret = -1;
+    }
+  else
+    {
+      if ((size_t) ret <= room)
+        {
+          /* The result has fit into room bytes.  */
+          buffer->length += (size_t) ret;
+          ret = 0;
+        }
+      else
+        {
+          /* The result was truncated.  Make more room, for a second 
vsnprintf()
+             call.  */
+          if (sb_ensure_more_bytes (buffer, (size_t) ret) < 0)
+            {
+              buffer->error = true;
+              ret = -1;
+            }
+          else
+            {
+              /* Second vsnprintf() call.  */
+              room = buffer->allocated - buffer->length;
+              ret = vsnprintf (buffer->data + buffer->length, room,
+                               formatstring, list_copy);
+              if (ret < 0)
+                {
+                  /* Failed.  */
+                  buffer->error = true;
+                  ret = -1;
+                }
+              else
+                {
+                  if ((size_t) ret <= room)
+                    {
+                      /* The result has fit into room bytes.  */
+                      buffer->length += (size_t) ret;
+                      ret = 0;
+                    }
+                  else
+                    /* The return values of the vsnprintf() calls are not
+                       consistent.  */
+                    abort ();
+                }
+            }
+        }
+    }
+
+  va_end (list_copy);
+  return ret;
+}
+
+int
+sb_appendf (struct string_buffer *buffer, const char *formatstring, ...)
+{
+  va_list args;
+
+  /* Make a bit of room, so that the probability that the first vsnprintf() 
call
+     succeeds is high.  */
+  size_t room = buffer->allocated - buffer->length;
+  if (room < 64)
+    {
+      if (sb_ensure_more_bytes (buffer, 64) < 0)
+        {
+          buffer->error = true;
+          return -1;
+        }
+      room = buffer->allocated - buffer->length;
+    }
+
+  va_start (args, formatstring);
+
+  /* First vsnprintf() call.  */
+  int ret = vsnprintf (buffer->data + buffer->length, room, formatstring, 
args);
+  if (ret < 0)
+    {
+      /* Failed.  */
+      buffer->error = true;
+      ret = -1;
+    }
+  else
+    {
+      if ((size_t) ret <= room)
+        {
+          /* The result has fit into room bytes.  */
+          buffer->length += (size_t) ret;
+          ret = 0;
+        }
+      else
+        {
+          /* The result was truncated.  Make more room, for a second 
vsnprintf()
+             call.  */
+          if (sb_ensure_more_bytes (buffer, (size_t) ret) < 0)
+            {
+              buffer->error = true;
+              ret = -1;
+            }
+          else
+            {
+              /* Second vsnprintf() call.  */
+              room = buffer->allocated - buffer->length;
+              va_end (args);
+              va_start (args, formatstring);
+              ret = vsnprintf (buffer->data + buffer->length, room,
+                               formatstring, args);
+              if (ret < 0)
+                {
+                  /* Failed.  */
+                  buffer->error = true;
+                  ret = -1;
+                }
+              else
+                {
+                  if ((size_t) ret <= room)
+                    {
+                      /* The result has fit into room bytes.  */
+                      buffer->length += (size_t) ret;
+                      ret = 0;
+                    }
+                  else
+                    /* The return values of the vsnprintf() calls are not
+                       consistent.  */
+                    abort ();
+                }
+            }
+        }
+    }
+
+  va_end (args);
+  return ret;
+}
diff --git a/lib/string-buffer.c b/lib/string-buffer.c
index 6ea589d67d..221cd9191e 100644
--- a/lib/string-buffer.c
+++ b/lib/string-buffer.c
@@ -21,7 +21,10 @@
 /* Specification.  */
 #include "string-buffer.h"
 
-#include <stdarg.h>
+/* Undocumented.  */
+extern int sb_ensure_more_bytes (struct string_buffer *buffer,
+                                 size_t increment);
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -38,7 +41,7 @@ sb_init (struct string_buffer *buffer)
 /* Ensures that INCREMENT bytes are available beyond the current used length
    of BUFFER.
    Returns 0, or -1 in case of out-of-memory error.  */
-static int
+int
 sb_ensure_more_bytes (struct string_buffer *buffer, size_t increment)
 {
   size_t incremented_length = buffer->length + increment;
@@ -91,165 +94,6 @@ sb_append (struct string_buffer *buffer, const char *str)
   return 0;
 }
 
-int
-sb_appendvf (struct string_buffer *buffer, const char *formatstring,
-             va_list list)
-{
-  va_list list_copy;
-
-  /* Make a bit of room, so that the probability that the first vsnprintf() 
call
-     succeeds is high.  */
-  size_t room = buffer->allocated - buffer->length;
-  if (room < 64)
-    {
-      if (sb_ensure_more_bytes (buffer, 64) < 0)
-        {
-          buffer->error = true;
-          return -1;
-        }
-      room = buffer->allocated - buffer->length;
-    }
-
-  va_copy (list_copy, list);
-
-  /* First vsnprintf() call.  */
-  int ret = vsnprintf (buffer->data + buffer->length, room, formatstring, 
list);
-  if (ret < 0)
-    {
-      /* Failed.  */
-      buffer->error = true;
-      ret = -1;
-    }
-  else
-    {
-      if ((size_t) ret <= room)
-        {
-          /* The result has fit into room bytes.  */
-          buffer->length += (size_t) ret;
-          ret = 0;
-        }
-      else
-        {
-          /* The result was truncated.  Make more room, for a second 
vsnprintf()
-             call.  */
-          if (sb_ensure_more_bytes (buffer, (size_t) ret) < 0)
-            {
-              buffer->error = true;
-              ret = -1;
-            }
-          else
-            {
-              /* Second vsnprintf() call.  */
-              room = buffer->allocated - buffer->length;
-              ret = vsnprintf (buffer->data + buffer->length, room,
-                               formatstring, list_copy);
-              if (ret < 0)
-                {
-                  /* Failed.  */
-                  buffer->error = true;
-                  ret = -1;
-                }
-              else
-                {
-                  if ((size_t) ret <= room)
-                    {
-                      /* The result has fit into room bytes.  */
-                      buffer->length += (size_t) ret;
-                      ret = 0;
-                    }
-                  else
-                    /* The return values of the vsnprintf() calls are not
-                       consistent.  */
-                    abort ();
-                }
-            }
-        }
-    }
-
-  va_end (list_copy);
-  return ret;
-}
-
-int
-sb_appendf (struct string_buffer *buffer, const char *formatstring, ...)
-{
-  va_list args;
-
-  /* Make a bit of room, so that the probability that the first vsnprintf() 
call
-     succeeds is high.  */
-  size_t room = buffer->allocated - buffer->length;
-  if (room < 64)
-    {
-      if (sb_ensure_more_bytes (buffer, 64) < 0)
-        {
-          buffer->error = true;
-          return -1;
-        }
-      room = buffer->allocated - buffer->length;
-    }
-
-  va_start (args, formatstring);
-
-  /* First vsnprintf() call.  */
-  int ret = vsnprintf (buffer->data + buffer->length, room, formatstring, 
args);
-  if (ret < 0)
-    {
-      /* Failed.  */
-      buffer->error = true;
-      ret = -1;
-    }
-  else
-    {
-      if ((size_t) ret <= room)
-        {
-          /* The result has fit into room bytes.  */
-          buffer->length += (size_t) ret;
-          ret = 0;
-        }
-      else
-        {
-          /* The result was truncated.  Make more room, for a second 
vsnprintf()
-             call.  */
-          if (sb_ensure_more_bytes (buffer, (size_t) ret) < 0)
-            {
-              buffer->error = true;
-              ret = -1;
-            }
-          else
-            {
-              /* Second vsnprintf() call.  */
-              room = buffer->allocated - buffer->length;
-              va_end (args);
-              va_start (args, formatstring);
-              ret = vsnprintf (buffer->data + buffer->length, room,
-                               formatstring, args);
-              if (ret < 0)
-                {
-                  /* Failed.  */
-                  buffer->error = true;
-                  ret = -1;
-                }
-              else
-                {
-                  if ((size_t) ret <= room)
-                    {
-                      /* The result has fit into room bytes.  */
-                      buffer->length += (size_t) ret;
-                      ret = 0;
-                    }
-                  else
-                    /* The return values of the vsnprintf() calls are not
-                       consistent.  */
-                    abort ();
-                }
-            }
-        }
-    }
-
-  va_end (args);
-  return ret;
-}
-
 void
 sb_free (struct string_buffer *buffer)
 {
diff --git a/modules/string-buffer b/modules/string-buffer
index 54da1db988..76c07d94ac 100644
--- a/modules/string-buffer
+++ b/modules/string-buffer
@@ -4,6 +4,7 @@ A buffer that accumulates a string by piecewise concatenation.
 Files:
 lib/string-buffer.h
 lib/string-buffer.c
+lib/string-buffer-printf.c
 
 Depends-on:
 stdbool
@@ -14,7 +15,7 @@ vsnprintf-posix
 configure.ac:
 
 Makefile.am:
-lib_SOURCES += string-buffer.c
+lib_SOURCES += string-buffer.c string-buffer-printf.c
 
 Include:
 "string-buffer.h"