I added JSON parsing code in GCC 15 to support sarif-replay.
In GCC 16 the aarch64 target has gained the ability to load tuning
information in JSON form via -muser-provided-CPU=FILENAME.json (see
r16-5615-g59f37983222d86 through r16-5619-ga0b8cc4a473e1e).
The UX is currently rather poor for malformed and invalid inputs to
-muser-provided-CPU=:
$ ./xgcc -B. -S test.c -muser-provided-CPU=malformed.json
cc1: error: error parsing JSON data: expected ':'; got number
$ ./xgcc -B. -S test.c -muser-provided-CPU=unsigned-3.json
cc1: warning: JSON tuning file does not contain version information;
compatibility cannot be verified
cc1: error: key ‘tune_params.sve_width’ value 5000000000 is out of range for
‘uint’ type [0, 4294967295]
cc1: error: validation failed for the provided JSON data
In particular it doesn't show location information within the JSON file.
A further JSON input to GCC is being considered via patch
"fmv: Add -ftarget-clones-table option support"
https://gcc.gnu.org/pipermail/gcc-patches/2026-February/708264.html
and that patch has similar issues with the diagnostics it emits on bad
input JSON.
This patch kit:
* moves some support code out from libgdiagnostics and sarif-replay so
that it can be used with global_dc,
* uses that to introduce a new json-diagnostic.{cc,h} to make it easy to
emit JSON diagnostics with location information from within GCC
* updates aarch64's -muser-provided-CPU= implementation to improve the
error handling.
With this patch, the above is improved to:
$ ./xgcc -B. -S test.c -muser-provided-CPU=malformed.json
malformed.json:3:17: error: error parsing JSON data: expected ':'; got number
3 | "sve_width" 128
| ^~~
$ ./xgcc -B. -S test.c -muser-provided-CPU=unsigned-3.json
cc1: warning: JSON tuning file does not contain version information;
compatibility cannot be verified
unsigned-3.json: In JSON value ‘/tune_params/sve_width’
unsigned-3.json:3:18: error: key ‘tune_params.sve_width’ value 5000000000 is
out of range for ‘uint’ type [0, 4294967295]
3 | "sve_width": 5000000000
| ^~~~~~~~~~
cc1: error: validation failed for the provided JSON data
showing file:line:column of the problematic JSON, quoting and
underlining the pertinent part of the input, and showing the
JSON Pointer of the relevant value, if there is one. This data is also
now captured by SARIF and HTML diagnostic sinks.
A similar approach could be adopted for the -ftarget-clones-table
patch to improve its diagnostics for bad input JSON.
The option -muser-provided-CPU= is new in GCC 16, but apparently is
intended purely for GCC developers. I'm not sure whether the fmv json
patch is aimed at GCC 16 or GCC 17, but it appears to be aimed at
end-users.
I'd like to push this to trunk now, but I appreciate that it's
non-trivial and not technically a fix of a regression, but it does add
UX polish.
I can self-approve the diagnostics/json refactorings.
aarch64 maintainers: are the aarch64 changes OK for trunk, either in
stage 4 or next stage 1?
Release managers: is this OK for stage 4, or should this wait until next
stage 1?
Thanks
Dave
David Malcolm (5):
diagnostics: use label_text for logical_location strings
diagnostics: split out physical_location_maker from libgdiagnostics
json: split out replayer_location_map from libsarifreplay.cc
Add json-diagnostic.{cc,h}
aarch64: improve diagnostics for bogus JSON tuning inputs [PR124094]
gcc/Makefile.in | 3 +-
.../aarch64-generate-json-tuning-routines.py | 17 +-
.../aarch64-json-tunings-parser-generated.inc | 428 +++++++++---------
.../aarch64/aarch64-json-tunings-parser.cc | 279 ++++++++----
gcc/diagnostics/client-data-hooks.h | 53 +++
gcc/diagnostics/context.cc | 5 +-
gcc/diagnostics/context.h | 4 +-
gcc/diagnostics/html-sink.cc | 11 +-
gcc/diagnostics/logical-locations.h | 6 +-
gcc/diagnostics/physical-location-maker.cc | 75 +++
gcc/diagnostics/physical-location-maker.h | 60 +++
gcc/diagnostics/sarif-sink.cc | 24 +-
gcc/diagnostics/selftest-logical-locations.cc | 18 +-
gcc/diagnostics/selftest-logical-locations.h | 6 +-
gcc/diagnostics/state-graphs-to-dot.cc | 15 +-
gcc/json-diagnostic.cc | 374 +++++++++++++++
gcc/json-diagnostic.h | 74 +++
gcc/json-parsing.cc | 1 +
gcc/json-parsing.h | 24 +
gcc/libgdiagnostics.cc | 62 +--
gcc/libsarifreplay.cc | 23 +-
.../aarch64/aarch64-json-tunings/boolean-2.c | 12 +-
.../aarch64-json-tunings/empty-brackets.c | 9 +-
.../aarch64/aarch64-json-tunings/enum-2.c | 19 +-
.../aarch64/aarch64-json-tunings/integer-2.c | 14 +-
.../aarch64/aarch64-json-tunings/integer-3.c | 13 +-
.../aarch64/aarch64-json-tunings/malformed.c | 11 +
.../aarch64-json-tunings/malformed.json | 5 +
.../aarch64/aarch64-json-tunings/string-2.c | 12 +-
.../aarch64-json-tunings/unidentified-key.c | 12 +-
.../aarch64/aarch64-json-tunings/unsigned-2.c | 10 +-
.../aarch64/aarch64-json-tunings/unsigned-3.c | 10 +-
gcc/tree-logical-location.cc | 26 +-
gcc/tree-logical-location.h | 6 +-
34 files changed, 1275 insertions(+), 446 deletions(-)
create mode 100644 gcc/diagnostics/physical-location-maker.cc
create mode 100644 gcc/diagnostics/physical-location-maker.h
create mode 100644 gcc/json-diagnostic.cc
create mode 100644 gcc/json-diagnostic.h
create mode 100644
gcc/testsuite/gcc.target/aarch64/aarch64-json-tunings/malformed.c
create mode 100644
gcc/testsuite/gcc.target/aarch64/aarch64-json-tunings/malformed.json
--
2.26.3
