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arch/x86: default CROSSDEV on a macOS host

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arch/x86 set CROSSDEV only under Cygwin, so everywhere else the build used
the bare tool names and got the host compiler.  On Linux that is a native
gcc which can produce i486 ELF objects, which is what the board README
assumes.  On macOS it is Apple clang, and on Apple Silicon that cannot
target i386 in any form -- so there is no configuration in which the default
works and a cross toolchain is not optional.

Default it to i686-elf-, which Homebrew packages and which accepts the
-march=i486 -mtune=i486 already in ARCHCPUFLAGS.  arch/x86_64 has had
exactly this stanza for its own toolchain all along; this is the same shape.

The Cygwin assignment becomes ?= to match, so that a CROSSDEV passed in from
the environment or the command line is honoured rather than overridden.

Note for anyone tempted by the toolchain they already have: a 64-bit x86
compiler with -m32 is not a substitute unless it was built with multilib.
Homebrew's x86_64-elf-gcc compiles 32-bit objects perfectly happily and has
no 32-bit libgcc to link them against, so the entire build succeeds and only
the final link fails, on __udivdi3, __divdi3, __moddi3 and __udivmoddi4.
`x86_64-elf-gcc -print-multi-lib' prints just `.;', which is the toolchain
saying so up front.

Signed-off-by: Marco Casaroli <marco.casaroli@gmail.com>

Assisted-by: Claude Opus 5 (1M context) <noreply@anthropic.com>
This commit is contained in:
Marco Casaroli 2026-07-27 05:05:44 +02:00
parent 564fae94d7
commit 89963644ab
1 changed files with 8 additions and 3 deletions
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11
arch/x86/src/common/Toolchain.defs
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@ -44,11 +44,16 @@ ARCHCPUFLAGS += -m32
LDFLAGS += -m elf_i386
endif
# We have to use a cross-development toolchain under Cygwin because the native
# Cygwin toolchains don't generate ELF binaries.
# A cross-development toolchain is required under Cygwin, whose native
# toolchains don't generate ELF binaries, and on macOS, which has no i386 host
# compiler at all -- Apple clang cannot target i386 on Apple Silicon.
# arch/x86_64 defaults CROSSDEV the same way. Note that a 64-bit toolchain
# with -m32 is not a substitute unless it was built with multilib.
ifeq ($(CONFIG_WINDOWS_CYGWIN),y)
CROSSDEV = i486-nuttx-elf-
CROSSDEV ?= i486-nuttx-elf-
else ifeq ($(CONFIG_HOST_MACOS),y)
CROSSDEV ?= i686-elf-
endif
CC = $(CROSSDEV)gcc