printf: reduce stack usage in the common case.

clang was inlining the function that creates a temporary on-stack buffer
for the unbuffered case.

Change-Id: I261f7ef09ed2939c66354aa245deb4e2e48d5dc6

Author: enh-google

libc/Android.bp

@@ -624,10 +624,12 @@ cc_library_static {
         "upstream-openbsd/lib/libc/string/wcslcpy.c",
         "upstream-openbsd/lib/libc/string/wcswidth.c",
 
-        // This file is originally from OpenBSD, and benefits from
-        // being compiled with openbsd-compat.h.
-        // TODO: clean this up instead.
+        // These files are originally from OpenBSD,
+        // and benefit from being compiled with openbsd-compat.h.
+        // TODO: clean them up instead.
         "bionic/fts.c",
+        "stdio/vfprintf.cpp",
+        "stdio/vfwprintf.cpp",
     ],
 
     // Each architecture has optimized versions of some routines,
@@ -686,9 +688,11 @@ cc_library_static {
 
     local_include_dirs: [
         "private",
-        "upstream-openbsd/android/include",
         "stdio",
-        "upstream-openbsd/lib/libc/include",
+        "upstream-openbsd/android/include/",
+        "upstream-openbsd/lib/libc/gdtoa/",
+        "upstream-openbsd/lib/libc/include/",
+        "upstream-openbsd/lib/libc/stdio/",
     ],
 
     name: "libc_openbsd",
@@ -698,8 +702,6 @@ cc_library_static {
     name: "libc_openbsd_large_stack",
     defaults: ["libc_defaults"],
     srcs: [
-        "stdio/vfprintf.cpp",
-        "stdio/vfwprintf.cpp",
         "upstream-openbsd/lib/libc/string/memmem.c",
         "upstream-openbsd/lib/libc/string/strstr.c",
     ],
@@ -710,11 +712,7 @@ cc_library_static {
     ],
 
     local_include_dirs: [
-        "private",
         "upstream-openbsd/android/include/",
-        "upstream-openbsd/lib/libc/gdtoa/",
-        "upstream-openbsd/lib/libc/include/",
-        "upstream-openbsd/lib/libc/stdio/",
     ],
 }
 

libc/stdio/printf_common.h

@@ -85,6 +85,10 @@ union arg {
 // Helper function for `fprintf to unbuffered unix file': creates a
 // temporary buffer.  We only work on write-only files; this avoids
 // worries about ungetc buffers and so forth.
+//
+// We prevent inlining because this massively increases the printf()
+// family's stack usage to support a rare case.
+__attribute__((__noinline__))
 static int __sbprintf(FILE* fp, const CHAR_TYPE* fmt, va_list ap) {
   FILE fake;
   struct __sfileext fakeext;