BUILD: sym: Make sure minidebug works correctly with most environments

Do not assume we're using GNU binutils when building the minidebug
section, so only use options most tools understand, and check if nm
actually exports the symbols in the format we expect.
Also do not use grep -F, as it doesn't exist on Solaris/Illumos, and we
don't actually need it.
This should help with github issue #3531.

diff --git a/Makefile b/Makefile
index d8ec26a8364f5c17b3d25c0fa2ea24d34e5ad011..469ed564047d77c173a0f1fc7ca47ea73eca93a2 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -581,8 +581,20 @@ EXTRA_OBJS =
 # compiler produces ELF objects, as the placeholders are ELF-specific. That
 # script appends the table to the program just linked, which moves nothing, so
 # it needs neither reserved room nor a second link.
+# Try to get something that works with most version of nm, objcopy and readelf.
+# This should work with GNU binutils, LLVM tools, elftoolchain, and OpenBSD's
+# nm.
 ifeq ($(origin USE_MINIDEBUG),undefined)
-USE_MINIDEBUG := $(if $(and $(shell command -v $(NM)),$(shell command -v $(OBJCOPY)),$(shell command -v $(READELF)),$(shell command -v $(XZ)),$(shell $(CC) -dM -E -xc - </dev/null 2>/dev/null | grep -F __ELF__)),1,)
+USE_MINIDEBUG := $(if $(and $(shell command -v $(XZ)),$(shell $(CC) -dM -E -xc - </dev/null 2>/dev/null | grep __ELF__),$(shell \
+       printf 'static int _probe_local;\nint _probe_global;\nint main(void){ return _probe_local + _probe_global; }\n' > .minidbg_probe.c && \
+       $(CC) -rdynamic .minidbg_probe.c -o .minidbg_probe >/dev/null 2>&1 && \
+       $(NM) -P .minidbg_probe 2>/dev/null | grep -q '^_probe_local ' && \
+       $(NM) -D -P .minidbg_probe 2>/dev/null | grep -q '^_probe_global ' && \
+       printf '_probe_global\n' > .minidbg_probe.syms && \
+       $(OBJCOPY) --only-keep-debug .minidbg_probe .minidbg_probe.dbg 2>/dev/null && \
+       $(OBJCOPY) -S --remove-section .comment --keep-symbols=.minidbg_probe.syms .minidbg_probe.dbg .minidbg_probe.mini 2>/dev/null && \
+       $(READELF) -hW -SW -lW .minidbg_probe >/dev/null 2>&1 && echo 1; \
+       rm -f .minidbg_probe.c .minidbg_probe .minidbg_probe.syms .minidbg_probe.dbg .minidbg_probe.mini)),1,)
 endif
 
 # This variable collects all USE_* values except those set to "implicit". This
@@ -1023,7 +1035,7 @@ endif
 # must not carry the decoder for nothing.
 # CRC64 support must be enabled as this is the integrity check that the "xz"
 # tool uses by default, and it also gates declarations in the public header.
-ifneq ($(shell $(CC) -dM -E -xc - </dev/null 2>/dev/null | grep -F __ELF__),)
+ifneq ($(shell $(CC) -dM -E -xc - </dev/null 2>/dev/null | grep __ELF__),)
 OPTIONS_CFLAGS += -DXZ_USE_CRC64
 OBJS += src/xz_dec_stream.o src/xz_dec_lzma2.o src/xz_crc32.o          \
         src/xz_crc64.o
@@ -1088,10 +1100,13 @@ endif # non-empty target
 # Only the last step can leave the program half-written, so it is the only one
 # whose failure is fatal; not being able to produce the table just leaves the
 # program without one, as happens when the tools do not know the target.
+# The nm options are spelled with their portable short forms (-P, -D) as some
+# implementations lack the long ones, and undefined symbols are told by their
+# type in awk instead of --defined-only, which these implementations lack too.
 define make_minidebug
        $(call qinfo,  MINIDBG)if ! ( \
-           $(NM) -D $@ --format=posix --defined-only | awk '{ print $$1 }' | sort > $@.dsyms && \
-           $(NM) $@ --format=posix --defined-only | awk '$$2 == "T" || $$2 == "t" { print $$1 }' | sort > $@.fsyms && \
+           $(NM) -D -P $@ | awk '$$2 != "U" && $$2 != "w" { print $$1 }' | sort > $@.dsyms && \
+           $(NM) -P $@ | awk '$$2 == "T" || $$2 == "t" { print $$1 }' | sort > $@.fsyms && \
            comm -13 $@.dsyms $@.fsyms > $@.ksyms && \
            $(OBJCOPY) --only-keep-debug $@ $@.dbg && \
            $(OBJCOPY) -S --remove-section .gdb_index --remove-section .comment --keep-symbols=$@.ksyms $@.dbg $@.mini && \