Place some hooks (__stdin, __stdout, __stderr) into libc for a future

ABI change.  There is some serious evilness here to work around some
gcc weaknesses.  We need to know the sizeof(FILE) manually until __sF
goes away in the next major bump.  We have the size for Alpha and i386,
missing is ia64, ppc and sparc* (and i386 with 64 bit longs).
At some point down the track we can change the stdin etc #defines to
stop hard coding the size of FILE into application binaries.

Lots of head scratching and ideas and testing by: green, imp

1 files changed, 23 insertions, 0 deletions

diff --git a/lib/libc/stdio/findfp.c b/lib/libc/stdio/findfp.c
index 4911400..3754258 100644
--- a/lib/libc/stdio/findfp.c
+++ b/lib/libc/stdio/findfp.c
@@ -77,6 +77,26 @@ FILE __sF[3] = {
 	std(__SWR|__SNBF, STDERR_FILENO)
 };
 
+/*
+ * The following kludge is done to ensure enough binary compatibility
+ * with future versions of libc.  Or rather it allows us to work with
+ * libraries that have been built with a newer libc that defines these
+ * symbols and expects libc to provide them.  We only have need to support
+ * i386 and alpha because they are the only "old" systems we have deployed.
+ */
+#if defined(__i386__)
+#define FILE_SIZE 88
+#elif defined(__alpha__)
+#define FILE_SIZE 152
+#endif
+#ifndef FILE_SIZE
+#error "You must define FILE_SIZE for this platform"
+#endif
+#define X(loc, sym)	__strong_reference(loc, sym)
+X(__sF + FILE_SIZE * 0, __stdin);
+X(__sF + FILE_SIZE * 1, __stdout);
+X(__sF + FILE_SIZE * 2, __stderr);
+
 struct glue __sglue = { &uglue, 3, __sF };
 static struct glue *lastglue = &uglue;
 
@@ -213,11 +233,14 @@ _cleanup()
 /*
  * __sinit() is called whenever stdio's internal variables must be set up.
  */
+#define SIZEMSG "WARNING: FILE_SIZE != sizeof(FILE)\n"
 void
 __sinit()
 {
 	int	i;
 
+	if (FILE_SIZE != sizeof(FILE))
+		write(2, SIZEMSG, sizeof(SIZEMSG) - 1);
 	THREAD_LOCK();
 	if (__sdidinit == 0) {
 		/* Set _extra for the usual suspects. */