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fix gcc ICEs and unresolved externs

PATCH In review Jeff Dike 1 participant 1 message Aug 1, 2008 User-mode Linux (UML)

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Jeff Dike

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PATCH 12/14 fix gcc ICEs and unresolved externs

From f9498bcc86dbf5249a4d9baff6ba508c3d4c86fa Mon Sep 17 00:00:00 2001

There are various constraints on the use of unit-at-a-time:
- i386 uses no-unit-at-a-time for pre-4.0 (not 4.3)
- x86_64 uses unit-at-a-time always

Uli reported a crash on x86_64 with gcc 4.1.2 with unit-at-a-time, resulting in commit c0a18111e571138747a98af18b3a2124df56a0d1

Ingo reported a gcc internal error with gcc 4.3 with no-unit-at-a-timem, resulting in 22eecde2f9034764a3fd095eecfa3adfb8ec9a98

Benny Halevy is seeing extern inlines not resolved with gcc 4.3 with no-unit-at-a-time

This patch reintroduces unit-at-a-time for gcc >= 4.0, bringing back the possibility of Uli's crash. If that happens, we'll debug it.

I started seeing both the internal compiler errors and unresolved inlines on Fedora 9. This patch fixes both problems, without so far reintroducing the crash reported by Uli.

Cc Benny Halevy <[email protected]>
Cc Adrian Bunk <[email protected]>
Cc Ingo Molnar <[email protected]>
Cc Ulrich Drepper <[email protected]>
---
 arch/um/Makefile        |    1 -
 arch/um/Makefile-i386   |    7 +++++++
 arch/um/Makefile-x86_64 |    3 +++
 3 files changed, 10 insertions(+), 1 deletions(-)
arch/um/Makefile +0 -1
index dbeab15..ca40397 100644
@@ -77,7 +77,6 @@ include $(srctree)/$(ARCH_DIR)/Makefile-os-$(OS)
 KERNEL_DEFINES = $(strip -Derrno=kernel_errno -Dsigprocmask=kernel_sigprocmask \
 			 -Dmktime=kernel_mktime $(ARCH_KERNEL_DEFINES))
 KBUILD_CFLAGS += $(KERNEL_DEFINES)
-KBUILD_CFLAGS += $(call cc-option,-fno-unit-at-a-time,)
 
 PHONY += linux
 
arch/um/Makefile-i386 +7 -0
index 561e373..302cbe5 100644
@@ -32,4 +32,11 @@ cflags-y += $(call cc-option,-mpreferred-stack-boundary=2)
 # an unresolved reference.
 cflags-y += -ffreestanding
 
+# Disable unit-at-a-time mode on pre-gcc-4.0 compilers, it makes gcc use
+# a lot more stack due to the lack of sharing of stacklots.  Also, gcc
+# 4.3.0 needs -funit-at-a-time for extern inline functions.
+KBUILD_CFLAGS += $(shell if [ $(call cc-version) -lt 0400 ] ; then \
+			echo $(call cc-option,-fno-unit-at-a-time); \
+			else echo $(call cc-option,-funit-at-a-time); fi ;)
+
 KBUILD_CFLAGS += $(cflags-y)
arch/um/Makefile-x86_64 +3 -0
index 8ed362f..a9cd7e7 100644
@@ -21,3 +21,6 @@ HEADER_ARCH := x86
 
 LINK-$(CONFIG_LD_SCRIPT_DYN) += -Wl,-rpath,/lib64
 LINK-y += -m64
+
+# Do unit-at-a-time unconditionally on x86_64, following the host
+KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)
Signature · 12 lines
1.5.5.1


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