[01/19] libctf: make it compile for old glibc

Message ID 20190716180420.236506-2-nick.alcock@oracle.com
State Superseded
Headers show
  • CTF linking support
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Commit Message

Nick Alcock July 16, 2019, 6:04 p.m.
From: Hans-Peter Nilsson <hp@bitrange.com>

With a glibc before 2.9 (such as 2.8), there's <endian.h> but no
htole64 or le64toh, so you get, compiling binutils for any target:

libtool: link: gcc -W -Wall -Wstrict-prototypes -Wmissing-prototypes \
-Wshadow -Werror -I/x/binutils/../zlib -g -O2 -o objdump \
objdump.o dwarf.o prdbg.o rddbg.o debug.o stabs.o rdcoff.o \
bucomm.o version.o filemode.o elfcomm.o  ../opcodes/.libs/libopcodes.a \
../libctf/libctf.a ../bfd/.libs/libbfd.a -L/x/obj/b/zlib -lz ../libiberty/libiberty.a -ldl
../libctf/libctf.a(ctf-archive.o): In function `ctf_archive_raw_iter_internal':
/x/src/libctf/ctf-archive.c:543: undefined reference to `le64toh'
/x/src/libctf/ctf-archive.c:550: undefined reference to `le64toh'
/x/src/libctf/ctf-archive.c:551: undefined reference to `le64toh'
/x/src/libctf/ctf-archive.c:551: undefined reference to `le64toh'
/x/src/libctf/ctf-archive.c:554: undefined reference to `le64toh'
../libctf/libctf.a(ctf-archive.o):/x/src/libctf/ctf-archive.c:545: more undefined references to `le64toh' follow

Also, I see no bswap_identity_64 *anywhere* except in libctf/swap.h
(including current glibc) and I don't think calling an "identity"-
function is better than just plain "#define foo(x) (x)" anyway.
(Where does the idea of a bytestap.h bswap_identity_64 come from?)

Speaking of that, I should mention that I instrumented the condition
to observe that the WORDS_BIGENDIAN case passes too for a presumed
big-endian target and glibc-2.8: there is a bswap_64 present for that
version.  Curiously, no test-case regressed with that instrumentation.

For the record, constructing binary blobs using text source to run
tests on, can be done by linking to --oformat binary (with most ELF
targets), but I guess that's seen as unnecessary roundabout perhaps
checking in binary files in the test-suite would be ok these days.

[nca: trimmed commit log slightly, updated changelog]

	* ctf-endian.h: Don't assume htole64 and le64toh are always
	present if HAVE_ENDIAN_H; also check if htole64 is defined.
	[! WORDS_BIGENDIAN] (htole64, le64toh): Define as identity,
	not bswap_identity_64.
 libctf/ctf-endian.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)



diff --git a/libctf/ctf-endian.h b/libctf/ctf-endian.h
index ec177d1bdd..f1cc527a08 100644
--- a/libctf/ctf-endian.h
+++ b/libctf/ctf-endian.h
@@ -24,10 +24,10 @@ 
 #include <stdint.h>
 #include "swap.h"
-#ifndef HAVE_ENDIAN_H
+#if !defined (HAVE_ENDIAN_H) || !defined (htole64)
-# define htole64(x) bswap_identity_64 ((x))
-# define le64toh(x) bswap_identity_64 ((x))
+# define htole64(x) (x)
+# define le64toh(x) (x)
 # define htole64(x) bswap_64 ((x))
 # define le64toh(x) bswap_64 ((x))