Developing the language

There is one compiler, written in flang itself and built into a binary. Working on it takes a clone and nothing else: the package has no dependencies, so the commands run straight after git clone.

A change to the compiler in flang/self/ must reprint the bootstrap point in the same commit, or bootstrap/ starts building the previous compiler silently:

sh scripts/bootstrap-reprint.sh           # reprint bootstrap/ (hours)
sh scripts/bootstrap-reprint.sh --check   # compare against the sources byte for byte, exit 1 on drift
sh scripts/bootstrap-reprint.sh --stroki  # under a second: every C string literal in the runtime is closed

The binary compiler itself does the printing (bootstrap/flang emit … --target c); if the binary is missing, the script builds it from bootstrap/ first.

The check re-emits and so costs what the print costs (hours), plus a make if the binary is not built. Call --check before merging a change under flang/self/ or flang/src/emit/c/, not on every save.

To try an edited compiler source on one program before a print, let the built binary interpret the sources: flang/self/bootstrap/check-with-source-compiler.flang checks one file with them and prints the proof report in words and the proof record. --trust skips the proof check of the compiler itself; a small program takes about ten minutes and 12 GiB:

bootstrap/flang run flang/self/bootstrap/check-with-source-compiler.flang \
  --function 'Проверить исходным компилятором' --trust --max-steps 2000000000 \
  --args "$(jq -n --arg path FILE --rawfile text FILE '{"путь": $path, "текст": $text}')"

The order of imports in that module matters: linking takes a module's declarations through whoever imports it first, together with that importer's только list, so «Compiler flang» comes first, as in compiler.flang. With «Печать в C» first, a checked program with требует stops at FLANG_UNKNOWN_NAME for «Печать значения».

The commands the language answers to:

# parse, type-check, prove totality
flang check docs/examples/leetcode/035-search-insert-position.flang --pretty

# run the examples declared inside the functions
flang test docs/examples/leetcode/035-search-insert-position.flang --pretty

# the same over a CORPUS: a directory or a glob instead of a file (binary only).
# Every failing example and every file not taken is named; the passing ones are
# a count. Exit code 0 — clean, 1 — something failed or a file was not taken,
# 2 — bad invocation.
flang test flang/stdlib/
flang test 'docs/examples/**/*.flang' --json

# call a function: --args takes a FLAT object of scalars, a list cannot go there
flang run docs/examples/leetcode/035-search-insert-position.flang \
  --function "Место вставки" --args '{"цель":2}'
# functions with a list argument are called by their own examples: flang test <file>

# print it — targets: c | cpp | csharp | elixir | go | java | js | python | rust | ts
flang emit docs/examples/leetcode/035-search-insert-position.flang \
  --target python --out ./out-python

Checks:

sh flang/test/обход.sh          # the walker's checks, run by the binary
sh flang/test/обход-примеров.sh # every example in the tree
sh scripts/bootstrap-reprint.sh --check  # the seed against what the sources emit
bootstrap/flang run-script                                  # every check in the tree, each with one line of explanation
bootstrap/flang run-script tests                            # the whole set at once

A single check is called by its name from that list: bootstrap/flang run-script specs:check, bootstrap/flang run-script links:check, bootstrap/flang run-script site:check. Each has its own exit code: 0 — clean, non-zero — the culprit is named.

Every command writes JSON to stdout, diagnostics to stderr, and returns non-zero on failure — the same contract everywhere, which is what makes it usable from CI, editors and agents. The one exception is flang repl, which talks to a human.