Command-line DEFINES suppresses the Makefile's _FILE_OFFSET_BITS append

[ChristopherA]

57fa48c5 ("Don't override DEFINES, but add to it.") changes container/update:11 from DEFINES="$DEFINES" to DEFINES+="$DEFINES". On the command line += does not have that effect: a command-line assignment suppresses a makefile's plain += whichever operator is used, so both forms drop src/Makefile:54's DEFINES+=-D_FILE_OFFSET_BITS=64.

Measured on an unmodified checkout at 57fa48c5, reading the first c++ -c line out of make -n:

invocation	-D_FILE_OFFSET_BITS=64
make	present
make DEFINES=-DFOO	dropped
make DEFINES+=-DFOO	dropped
make DEFINES+=	dropped

The two middle rows are byte-identical compile lines, so the commit changes nothing. The last row shows why: an empty command-line DEFINES+= drops the flag too, so no value is involved -- it is the assignment's origin that suppresses the makefile's append.

Two environments, identical results, so this is not an artifact of one make generation:

• Debian 12 (bookworm), aarch64, GNU Make 4.3, g++ 12.2.0. HOST auto-detects as LINUX, so the table is exactly what runs.
• macOS 26.5.1, arm64, GNU Make 3.81, Apple clang 21. HOST is DARWIN here, so reaching the branch needs HOST=LINUX on the command line; every row then matches Debian's.

override DEFINES += at src/Makefile:54 and :62 fixes it -- same checkouts, that edit and nothing else:

invocation	-D_FILE_OFFSET_BITS=64
make	present
make DEFINES=-DFOO	present
make DEFINES+=-DFOO	present

and make DEFINES=-DFOO then carries both -DFOO and -D_FILE_OFFSET_BITS=64, so the override does not clobber the caller's own defines. Identical on both make versions.

Scope, which is narrower than it first looks, and I would rather state it than have you find it. container/Dockerfile is FROM alpine:3.13, and musl does not consult _FILE_OFFSET_BITS at all: on alpine:3.13.12 with musl-dev installed, 0 of 217 headers reference it, against 14 that mention off_t. So the container is unaffected either way and 57fa48c5 is inert there rather than harmful. What remains is the Makefile behaviour itself, which matters to anyone passing DEFINES on the command line for a 32-bit glibc or Solaris build, where that append is what sets a 64-bit off_t.

That is how this surfaced: the wider-index recipe in #100 passes DEFINES on the command line, which silently drops the append on those targets, so our own Linux builds restate -D_FILE_OFFSET_BITS=64 by hand.

One inconsistency in the same commit, whatever you decide about the above: it changes only the dgd line at :11. The lpc-ext line at :13 still reads DEFINES="$DEFINES", so even granting the operator behaved as intended, the change would be half-applied within its own file.

[dworkin]

Somehow I confused myself into thinking that 57fa48c5 worked. b4da6a9 should fix it.

[ChristopherA]

Thanks for the fix.

Confirmed at b4da6a96, measured on an unmodified checkout of this repository at that commit.

Debian 12 (aarch64), GNU Make 4.3, g++ 12.2.0. Building with a command-line DEFINES:

make DEFINES='-DUINDEX_TYPE="unsigned int" -DUINDEX_MAX=UINT_MAX' install

At 57fa48c5, none of the 53 compile lines carry -D_FILE_OFFSET_BITS=64, and the string does not appear anywhere in the build log. At b4da6a96, all 53 carry it:

c++ -pthread -I. -Icomp -Ilex -Ied -Iparser -Ikfun -DLINUX -DUINDEX_TYPE="unsigned int" -DUINDEX_MAX=UINT_MAX -D_FILE_OFFSET_BITS=64 -g -DDEBUG   -c -o alloc.o alloc.cpp

A plain make is unaffected on that host: the default build produces a byte-identical .text and the same dynamic symbol table across the two commits, so the change is a no-op there for anyone not overriding DEFINES.

It also repairs the incantation in your closing comment on #100, which seems worth mentioning because that issue is closed and is what a reader will copy from:

make DEFINES+='-DUINDEX_TYPE="unsigned int" -DUINDEX_MAX=UINT_MAX -DSSIZET_TYPE="unsigned int" -DSSIZET_MAX=1048576'

Run verbatim it splits the same way, 0 of 53 compile lines carrying the large-file flag at 57fa48c5 and 53 of 53 at b4da6a96. Not because += now appends from the command line -- it still does not -- but because the platform appends target a variable the command line does not set, so there is nothing left to suppress. Both builds cold-boot to Initialization complete and accept swap_size = 200000, which a stock build refuses with Config error: int value out of range.