1# Checklist for making changes to `libpldm` 2 3## Philosophy and influences 4 5- [Good Practices in Library Design, Implementation, and Maintenance - Ulrich 6 Drepper][goodpractice] 7 8[goodpractice]: https://www.akkadia.org/drepper/goodpractice.pdf 9 10- [How Do I Make This Hard to Misuse? - Rusty Russell][rusty-api-scale-good] 11 12[rusty-api-scale-good]: https://ozlabs.org/~rusty/index.cgi/tech/2008-03-30.html 13 14- [What If I Don't Actually Like My Users? - Rusty Russell][rusty-api-scale-bad] 15 16[rusty-api-scale-bad]: https://ozlabs.org/~rusty/index.cgi/tech/2008-04-01.html 17 18- [Red flags that indicate questionable quality - Lennart 19 Poettering][poettering-library-red-flags] 20 21[poettering-library-red-flags]: 22 https://mastodon.social/@pid_eins/112517953375791453 23 24- [Not sure if this is a gcc bug or some weird corner of UB or what... - Andrew 25 Zonenberg][azonenberg-packed-struct] 26 27[azonenberg-packed-struct]: https://ioc.exchange/@azonenberg/112535511250395148 28 29## References 30 31- [C17 draft standard][c17-draft-standard] 32 33[c17-draft-standard]: 34 https://web.archive.org/web/20181230041359if_/http://www.open-std.org/jtc1/sc22/wg14/www/abq/c17_updated_proposed_fdis.pdf 35 36## Definitions 37 38- **Error condition**: An invalid state reached at runtime, caused either by 39 resource exhaustion, or incorrect use of the library's public APIs and data 40 types. 41 42- **Invariant**: A condition in the library's implementation that must never 43 evaluate false. 44 45- **Public API**: Any definitions and declarations under `include/libpldm`. 46 47- **Wire format**: Any message structure defined in the DMTF PLDM protocol 48 specifications. 49 50## Elaborations 51 52- Resource exhaustion is always an error condition and never an invariant 53 violation. 54 55- An invariant violation is always a programming failure of the library's 56 implementation, and never the result of incorrect use of the library's public 57 APIs (see error condition). 58 59- Corollaries of the above two points: 60 61 - Incorrect use of public API functions is always an error condition, and is 62 dealt with by returning an error code. 63 64 - Incorrect use of static functions in the library's implementation is an 65 invariant violation which may be established using `assert()`. 66 67- `assert()` is the recommended way to demonstrate invariants are upheld. 68 69## Adding a new API 70 71- [ ] My new public `struct` definitions are _not_ marked 72 `__attribute__((packed))` 73 74- [ ] My new public `struct` definitions do _not_ define a flexible array 75 member, unless: 76 77 - [ ] It's contained in an `#ifndef __cplusplus` macro guard, as flexible 78 arrays are not specified by C++, and 79 80 - [ ] I've implemented an accessor function so the array base pointer can be 81 accessed from C++, and 82 83 - [ ] It is defined as per the C17 specification by omitting the length[^1] 84 85 - Note: Any array defined with length 1 is _not_ a flexible array, and any 86 access beyond the first element invokes undefined behaviour in both C and 87 C++. 88 89[^1]: 90 [C17 draft specification][c17-draft-standard], 6.7.2.1 Structure and union 91 specifiers, paragraph 18. 92 93- [ ] If my work interacts with the PLDM wire format, then I have done so using 94 the `msgbuf` APIs found in `src/msgbuf.h` (and under `src/msgbuf/`) to 95 minimise concerns around spatial memory safety and endian-correctness. 96 97- [ ] All my error conditions are handled by returning an error code to the 98 caller. 99 100- [ ] All my invariants are tested using `assert()`. 101 102- [ ] I have not used `assert()` to evaluate any error conditions without also 103 handling the error condition by returning an error code the the caller. 104 105 - Release builds of the library are configured with `assert()` disabled 106 (`-Db_ndebug=if-release`, which provides `-DNDEBUG` in `CFLAGS`). 107 108- [ ] My new APIs return negative `errno` values on error and not PLDM 109 completion codes. 110 111 - [ ] The specific error values my function returns and their meaning in the 112 context of the function call are listed in the API documentation. 113 114- [ ] If I've added support for a new PLDM message type, then I've implemented 115 both the encoder and decoder for that message. Note this applies for both 116 request _and_ response message types. 117 118- [ ] My new function symbols are marked with `LIBPLDM_ABI_TESTING` in the 119 implementation 120 121- [ ] I've implemented test cases with reasonable branch coverage of each new 122 function I've added 123 124- [ ] I've guarded the test cases of functions marked `LIBPLDM_ABI_TESTING` so 125 that they are not compiled when the corresponding function symbols aren't 126 visible 127 128- [ ] If I've added support for a new message type, then my commit message 129 specifies all of: 130 131 - [ ] The relevant DMTF specification by its DSP number and title 132 - [ ] The relevant version of the specification 133 - [ ] The section of the specification that defines the message type 134 135- [ ] If my work impacts the public API of the library, then I've added an entry 136 to `CHANGELOG.md` describing my work 137 138## Stabilising an existing API 139 140- [ ] The API of interest is currently marked `LIBPLDM_ABI_TESTING` 141 142- [ ] My commit message links to a publicly visible patch that makes use of the 143 API 144 145- [ ] My commit updates the annotation from `LIBPLDM_ABI_TESTING` to 146 `LIBPLDM_ABI_STABLE` only for the function symbols demonstrated by the 147 patch linked in the commit message. 148 149- [ ] I've removed guards from the function's tests so they are always compiled 150 151- [ ] If I've updated the ABI dump, then I've used the OpenBMC CI container to 152 do so. 153 154## Updating an ABI dump 155 156Each of the following must succeed: 157 158- [ ] Enter the OpenBMC CI Docker container 159 - Approximately: 160 `docker run --cap-add=sys_admin --rm=true --privileged=true -u $USER -w $(pwd) -v $(pwd):$(pwd) -e MAKEFLAGS= -it openbmc/ubuntu-unit-test:2024-W21-ce361f95ff4fa669` 161- [ ] `CC=gcc CXX=g++; [ $(uname -m) = 'x86_64' ] && meson setup -Dabi=deprecated,stable build` 162- [ ] `meson compile -C build` 163- [ ] `./scripts/abi-dump-formatter < build/src/current.dump > abi/x86_64/gcc.dump` 164 165## Removing an API 166 167- [ ] If the function is marked `LIBPLDM_ABI_TESTING`, then I have removed it 168 169- [ ] If the function is marked `LIBPLDM_ABI_STABLE`, then I have changed the 170 annotation to `LIBPLDM_ABI_DEPRECATED` and left it in-place. 171 172- [ ] If the function is marked `LIBPLDM_ABI_DEPRECATED`, then I have removed it 173 only after satisfying myself that each of the following is true: 174 175 - [ ] There are no known users of the function left in the community 176 - [ ] There has been at least one tagged release of `libpldm` subsequent to 177 the API being marked deprecated 178 179## Renaming an API 180 181A change to an API is a pure rename only if there are no additional behavioural 182changes. Renaming an API with no other behavioural changes is really two 183actions: 184 1851. Introducing the new API name 1862. Deprecating the old API name 187 188- [ ] Only the name of the function has changed. None of its behaviour has 189 changed. 190 191- [ ] Both the new and the old functions are declared in the public headers 192 193- [ ] I've aliased the old function name to the new function name via the 194 `libpldm_deprecated_aliases` list in `meson.build` 195 196- [ ] I've added a [semantic patch][coccinelle] to migrate users from the old 197 name to the new name 198 199[coccinelle]: https://coccinelle.gitlabpages.inria.fr/website/ 200 201## Testing my changes 202 203Each of the following must succeed when executed in order. Note that to avoid 204[googletest bug #4232][googletest-issue-4232] you must avoid using GCC 12 205(shipped in Debian Bookworm). 206 207[googletest-issue-4232]: https://github.com/google/googletest/issues/4232 208 209- [ ] `meson setup -Dabi-compliance-check=disabled build` 210- [ ] `meson compile -C build && meson test -C build` 211 212- [ ] `meson configure --buildtype=release build` 213- [ ] `meson compile -C build && meson test -C build` 214 215- [ ] `meson configure --buildtype=debug build` 216- [ ] `meson configure -Dabi=deprecated,stable build` 217- [ ] `meson compile -C build && meson test -C build` 218 219This process is captured in `scripts/pre-submit` for automation. 220