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Extend tools/macro_builder to also generate DOUBLE_PASTE and TYPE_BODY

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tools/macro_builder only emitted NLOHMANN_JSON_EXPAND..PASTE64, so two
other tables that scale with the same max_args stayed hand-maintained
with nothing checking them: NLOHMANN_JSON_DOUBLE_PASTE (added by hand
in #4563 for the *_WITH_NAMES macros) and the 64-slot dispatch table of
NLOHMANN_JSON_TYPE_BODY (the #4041 zero-member/one-or-more-member
switch). Both tables pass one macro name per slot to the same
NLOHMANN_JSON_GET_MACRO dispatch as PASTE, so they can drift out of
sync with max_args exactly the way _dp did in the ABI tag list fixed
by #5544.

Extend main.cpp with build_double_paste_code() (same recursive-doubling
shape as build_paste_code(), but DOUBLE_PASTE consumes two arguments
per member, so an even slot index falls back to the next lower odd
DOUBLE_PASTE<N>) and build_type_body_table() (max_args - 1 MEMBERS
slots and one trailing EMPTY slot, 8 per line, matching how it is
written by hand today). Add a "type_body" argument that selects the
TYPE_BODY block, since it lives at a separate location in
macro_scope.hpp from the EXPAND..DOUBLE_PASTE63 block; plain invocation
is unchanged apart from covering the extended range. No longer emit
the tool's old trailing blank line, so its output is directly diffable
without post-processing.

Verified with c++ -std=c++11: running the tool (with and without
"type_body") and piping the raw output through the pinned astyle
reproduces both blocks of the current macro_scope.hpp byte for byte.
tests/src/unit-udt_macro.cpp (all NLOHMANN_DEFINE_TYPE_*/_WITH_NAMES/
zero-member variants) passes unchanged under -std=c++11 and -std=c++17
with -fsanitize=address,undefined.

Add a "macro_builder_check" Makefile target that builds main.cpp,
regenerates both blocks into a scratch directory inside the repository
(astyle's --project lookup needs the target files under the same tree
as .astylerc, unlike an external /tmp directory), and diffs them
against the corresponding ranges of macro_scope.hpp; wire it into
check-amalgamation next to the natvis check. Wire the same regeneration
into check_amalgamation.yml, splicing the (still unindented) generated
blocks back into the PR's own macro_scope.hpp before the existing
astyle/amalgamation step runs, so that step's own tree-wide astyle
pass both indents them and folds any drift into the amalgamation
patch/diff the workflow already produces.

Unlike amalgamate.py and generate_natvis.py, this step builds
tools/macro_builder/main.cpp from the pull request's own checkout
($MAIN_DIR) rather than a separate checkout of tools/ at develop: this
tool has no independent source of truth to regenerate against (its
README documents that it must reproduce macro_scope.hpp byte for
byte), so a develop-pinned copy would only reproduce the
generate_natvis.py trap fixed in a previous commit on this branch,
where a PR that teaches the tool to cover more of the file fails its
own CI until that PR merges and updates the develop copy.

Add tools/macro_builder/README.md documentation for both new tables
and the two-invocation usage, and a short pointer comment above
NLOHMANN_JSON_TYPE_BODY (the EXPAND pointer already covered the first
block; extended its wording to include DOUBLE_PASTE63).

Closes #5717 item 5 in full, completing what the documentation-only
"Document tools/macro_builder..." commit already on this branch left
open (that commit's README/pointer-comment half stands; it also covers
item 7).

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
This commit is contained in:
Niels Lohmann
2026-09-30 18:35:18 +02:00
parent a436ba2775
commit 7aeb98414e
6 changed files with 167 additions and 27 deletions
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.github/workflows/check_amalgamation.yml
+39
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@@ -65,6 +65,45 @@ jobs:
- name: Install generate_natvis dependencies
run: pip3 install -r $NATVIS_TOOL_DIR/requirements.txt
- name: Regenerate the tools/macro_builder tables in macro_scope.hpp
run: |
cd $MAIN_DIR
# Built from this PR's own tools/macro_builder/main.cpp, not a
# develop checkout: unlike amalgamate.py and generate_natvis.py,
# this tool has no other source of truth to check against (its
# own README documents that it must reproduce macro_scope.hpp
# byte for byte), so there is nothing to gain from checking out a
# separate copy, and doing so would make this step fail on a PR
# that adds support for a new dispatch table until that PR itself
# merges to develop, the same way generate_natvis.py's --version
# requirement briefly did.
TMPDIR=$(mktemp -d ./macro_builder_check.XXXXXX)
c++ -std=c++11 tools/macro_builder/main.cpp -o "$TMPDIR/macro_builder"
"$TMPDIR/macro_builder" > "$TMPDIR/paste.hpp"
"$TMPDIR/macro_builder" type_body > "$TMPDIR/type_body.hpp"
# Splice the (still unindented) generated blocks back into
# macro_scope.hpp; the astyle pass below indents their
# continuation lines the same way it does for the rest of
# include/, so a correctly regenerated file comes out unchanged.
awk -v newfile="$TMPDIR/paste.hpp" '
BEGIN { while ((getline line < newfile) > 0) { new = new line "\n" } }
/^#define NLOHMANN_JSON_EXPAND\( x \) x$/ { printf "%s", new; skip=1 }
skip && /^#define NLOHMANN_JSON_DOUBLE_PASTE63\(/ { skip=0; next }
skip { next }
{ print }
' include/nlohmann/detail/macro_scope.hpp > "$TMPDIR/macro_scope_1.hpp"
awk -v newfile="$TMPDIR/type_body.hpp" '
BEGIN { while ((getline line < newfile) > 0) { new = new line "\n" } }
/^#define NLOHMANN_JSON_TYPE_BODY\(Prefix, \.\.\.\)/ { printf "%s", new; skip=1 }
skip && /^[[:space:]]*NLOHMANN_JSON_TYPE_BODY_SENTINEL\)\)$/ { skip=0; next }
skip { next }
{ print }
' "$TMPDIR/macro_scope_1.hpp" > "$TMPDIR/macro_scope_2.hpp"
mv "$TMPDIR/macro_scope_2.hpp" include/nlohmann/detail/macro_scope.hpp
rm -rf "$TMPDIR"
- name: Regenerate amalgamation, formatting, and BUILD.bazel
run: |
cd $MAIN_DIR