From: Sergei Trofimovich <siarh...@google.com>
To build `libc` for a target one needs to build `gcc` without `libc`
support first. Commit r14-4823-g8abddb187b3348 "libgcc: support
heap-based trampolines" added unconditional `libc` dependency and broke
libc-less `gcc` builds.
An example failure on `x86_64-unknown-linux-gnu`:
$ mkdir -p /tmp/empty
$ ../gcc/configure \
--disable-multilib \
--without-headers \
--with-newlib \
--enable-languages=c \
--disable-bootstrap \
--disable-gcov \
--disable-threads \
--disable-shared \
--disable-libssp \
--disable-libquadmath \
--disable-libgomp \
--disable-libatomic \
--with-build-sysroot=/tmp/empty
$ make
...
/tmp/gb/./gcc/xgcc -B/tmp/gb/./gcc/ -B/usr/local/x86_64-pc-linux-gnu/bin/
-B/usr/local/x86_64-pc-linux-gnu/lib/ -isystem
/usr/local/x86_64-pc-linux-gnu/include -isystem
/usr/local/x86_64-pc-linux-gnu/sys-include --sysroot=/tmp/empty -g -O2 -O2
-g -O2 -DIN_GCC -W -Wall -Wno-narrowing -Wwrite-strings -Wcast-qual
-Wstrict-prototypes -Wmissing-prototypes -Wold-style-definition -isystem
./include -fpic -mlong-double-80 -DUSE_ELF_SYMVER -fcf-protection -mshstk -g
-DIN_LIBGCC2 -fbuilding-libgcc -fno-stack-protector -Dinhibit_libc -fpic
-mlong-double-80 -DUSE_ELF_SYMVER -fcf-protection -mshstk -I. -I. -I../.././gcc
-I/home/slyfox/dev/git/gcc/libgcc -I/home/slyfox/dev/git/gcc/libgcc/.
-I/home/slyfox/dev/git/gcc/libgcc/../gcc
-I/home/slyfox/dev/git/gcc/libgcc/../include -DHAVE_CC_TLS -DUSE_TLS -o
heap-trampoline.o -MT heap-trampoline.o -MD -MP -MF heap-trampoline.dep -c
.../gcc/libgcc/config/i386/heap-trampoline.c -fvisibility=hidden -DHIDE_EXPORTS
../gcc/libgcc/config/i386/heap-trampoline.c:3:10: fatal error: unistd.h: No
such file or directory
3 | #include <unistd.h>
| ^~~~~~~~~~
compilation terminated.
make[2]: *** [.../gcc/libgcc/static-object.mk:17: heap-trampoline.o] Error 1
make[2]: Leaving directory '/tmp/gb/x86_64-pc-linux-gnu/libgcc'
make[1]: *** [Makefile:13307: all-target-libgcc] Error 2
The change inhibits any heap-based trampoline code.
libgcc/
* libgcc/config/aarch64/heap-trampoline.c: Disable when libc is
not present.
---
libgcc/config/aarch64/heap-trampoline.c | 5 +++++
libgcc/config/i386/heap-trampoline.c | 5 +++++
2 files changed, 10 insertions(+)
diff --git a/libgcc/config/aarch64/heap-trampoline.c
b/libgcc/config/aarch64/heap-trampoline.c
index c8b83681ed7..f22233987ca 100644
--- a/libgcc/config/aarch64/heap-trampoline.c
+++ b/libgcc/config/aarch64/heap-trampoline.c
@@ -1,5 +1,8 @@
/* Copyright The GNU Toolchain Authors. */
+/* libc is required to allocate trampolines. */
+#ifndef inhibit_libc
+
#include <unistd.h>
#include <sys/mman.h>
#include <stdint.h>
@@ -170,3 +173,5 @@ __builtin_nested_func_ptr_deleted (void)
tramp_ctrl_curr = prev;
}
}
+
+#endif /* !inhibit_libc */
diff --git a/libgcc/config/i386/heap-trampoline.c
b/libgcc/config/i386/heap-trampoline.c
index 96e13bf828e..4b9f4365868 100644
--- a/libgcc/config/i386/heap-trampoline.c
+++ b/libgcc/config/i386/heap-trampoline.c
@@ -1,5 +1,8 @@
/* Copyright The GNU Toolchain Authors. */
+/* libc is required to allocate trampolines. */
+#ifndef inhibit_libc
+
#include <unistd.h>
#include <sys/mman.h>
#include <stdint.h>
@@ -170,3 +173,5 @@ __builtin_nested_func_ptr_deleted (void)
tramp_ctrl_curr = prev;
}
}
+
+#endif /* !inhibit_libc */
--
2.42.0
