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- [The Good, the Bad, and the Weird - Trail of Bits 30 Blog][trail-of-bits-weird-machines] 31 32[trail-of-bits-weird-machines]: 33 https://blog.trailofbits.com/2018/10/26/the-good-the-bad-and-the-weird/ 34 35- [Logic for Programmers - Hillel Wayne][logic-for-programmers] 36 37[logic-for-programmers]: https://leanpub.com/logic 38 39- [Parse, don’t validate - Alexis King][alexis-king-parse-dont-validate] 40 41[alexis-king-parse-dont-validate]: 42 https://lexi-lambda.github.io/blog/2019/11/05/parse-don-t-validate/ 43 44## References 45 46- [C17 draft standard][c17-draft-standard] 47 48[c17-draft-standard]: 49 https://web.archive.org/web/20181230041359if_/http://www.open-std.org/jtc1/sc22/wg14/www/abq/c17_updated_proposed_fdis.pdf 50 51- [SEI CERT C Coding Standard][sei-cert-c-coding-standard] 52 53[sei-cert-c-coding-standard]: 54 https://wiki.sei.cmu.edu/confluence/display/c/SEI+CERT+C+Coding+Standard 55 56- [Common Weakness Enumeration (CWE) - Software 57 Development][common-weakness-enumeration-sw] 58 59[common-weakness-enumeration-sw]: 60 https://cwe.mitre.org/data/definitions/699.html 61 62## Definitions 63 64- **Error condition**: An invalid state reached at runtime, caused either by 65 resource exhaustion, or incorrect use of the library's public APIs and data 66 types. 67 68- **Invariant**: A condition in the library's implementation that must never 69 evaluate false. 70 71- **Public API**: Any definitions and declarations under `include/libpldm`. 72 73- **Wire format**: Any message structure defined in the DMTF PLDM protocol 74 specifications. 75 76## Elaborations 77 78- Resource exhaustion is always an error condition and never an invariant 79 violation. 80 81- An invariant violation is always a programming failure of the library's 82 implementation, and never the result of incorrect use of the library's public 83 APIs (see error condition). 84 85- Corollaries of the above two points: 86 87 - Incorrect use of public API functions is always an error condition, and is 88 dealt with by returning an error code. 89 90 - Incorrect use of static functions in the library's implementation is an 91 invariant violation which may be established using `assert()`. 92 93- `assert()` is the recommended way to demonstrate invariants are upheld. 94 95## Adding a new API 96 97- [ ] My new public `struct` definitions are _not_ marked 98 `__attribute__((packed))` 99 100- [ ] My new public `struct` definitions do _not_ define a flexible array 101 member, unless: 102 103 - [ ] It's contained in an `#ifndef __cplusplus` macro guard, as flexible 104 arrays are not specified by C++, and 105 106 - [ ] I've implemented an accessor function so the array base pointer can be 107 accessed from C++, and 108 109 - [ ] It is defined as per the C17 specification by omitting the length[^1] 110 111 - Note: Any array defined with length 1 is _not_ a flexible array, and any 112 access beyond the first element invokes undefined behaviour in both C and 113 C++. 114 115 - [ ] I've annotated the flexible array member with `LIBPLDM_CC_COUNTED_BY()` 116 117[^1]: 118 [C17 draft specification][c17-draft-standard], 6.7.2.1 Structure and union 119 specifiers, paragraph 18. 120 121- [ ] If my work interacts with the PLDM wire format, then I have done so using 122 the `msgbuf` APIs found in `src/msgbuf.h` (and under `src/msgbuf/`) to 123 minimise concerns around spatial memory safety and endian-correctness. 124 125- [ ] All my error conditions are handled by returning an error code to the 126 caller. 127 128- [ ] All my invariants are tested using `assert()`. 129 130- [ ] I have not used `assert()` to evaluate any error conditions without also 131 handling the error condition by returning an error code the the caller. 132 133 - Release builds of the library are configured with `assert()` disabled 134 (`-Db_ndebug=if-release`, which provides `-DNDEBUG` in `CFLAGS`). 135 136- [ ] My new APIs return negative `errno` values on error and not PLDM 137 completion codes. 138 139 - [ ] The specific error values my function returns and their meaning in the 140 context of the function call are listed in the API documentation. 141 142- [ ] If I've added support for a new PLDM message type, then I've implemented 143 both the encoder and decoder for that message. Note this applies for both 144 request _and_ response message types. 145 146- [ ] My new function symbols are marked with `LIBPLDM_ABI_TESTING` in the 147 implementation 148 149- [ ] I've implemented test cases with reasonable branch coverage of each new 150 function I've added 151 152- [ ] I've guarded the test cases of functions marked `LIBPLDM_ABI_TESTING` so 153 that they are not compiled when the corresponding function symbols aren't 154 visible 155 156- [ ] If I've added support for a new message type, then my commit message 157 specifies all of: 158 159 - [ ] The relevant DMTF specification by its DSP number and title 160 - [ ] The relevant version of the specification 161 - [ ] The section of the specification that defines the message type 162 163- [ ] If my work impacts the public API of the library, then I've added an entry 164 to `CHANGELOG.md` describing my work 165 166## Stabilising an existing API 167 168- [ ] The API of interest is currently marked `LIBPLDM_ABI_TESTING` 169 170- [ ] My commit message links to a publicly visible patch that makes use of the 171 API 172 173- [ ] My commit updates the annotation from `LIBPLDM_ABI_TESTING` to 174 `LIBPLDM_ABI_STABLE` only for the function symbols demonstrated by the 175 patch linked in the commit message. 176 177- [ ] I've removed guards from the function's tests so they are always compiled 178 179- [ ] If I've updated the ABI dump, then I've used the OpenBMC CI container to 180 do so. 181 182## Updating an ABI dump 183 184Each of the following must succeed: 185 186- [ ] Enter the OpenBMC CI Docker container 187 - Approximately: 188 `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` 189- [ ] `CC=gcc CXX=g++; [ $(uname -m) = 'x86_64' ] && meson setup -Dabi=deprecated,stable build` 190- [ ] `meson compile -C build` 191- [ ] `./scripts/abi-dump-formatter < build/src/current.dump > abi/x86_64/gcc.dump` 192 193## Removing an API 194 195- [ ] If the function is marked `LIBPLDM_ABI_TESTING`, then I have removed it 196 197- [ ] If the function is marked `LIBPLDM_ABI_STABLE`, then I have changed the 198 annotation to `LIBPLDM_ABI_DEPRECATED` and left it in-place. 199 200 - [ ] I have updated the ABI dump, or will mark the change as WIP until it has 201 been. 202 203- [ ] If the function is marked `LIBPLDM_ABI_DEPRECATED`, then I have removed it 204 only after satisfying myself that each of the following is true: 205 206 - [ ] There are no known users of the function left in the community 207 - [ ] There has been at least one tagged release of `libpldm` subsequent to 208 the API being marked deprecated 209 210## Renaming an API 211 212A change to an API is a pure rename only if there are no additional behavioural 213changes. Renaming an API with no other behavioural changes is really two 214actions: 215 2161. Introducing the new API name 2172. Deprecating the old API name 218 219- [ ] Only the name of the function has changed. None of its behaviour has 220 changed. 221 222- [ ] Both the new and the old functions are declared in the public headers 223 224- [ ] I've aliased the old function name to the new function name via the 225 `libpldm_deprecated_aliases` list in `meson.build` 226 227- [ ] I've added a [semantic patch][coccinelle] to migrate users from the old 228 name to the new name 229 230[coccinelle]: https://coccinelle.gitlabpages.inria.fr/website/ 231 232- [ ] I've updated the ABI dump to capture the rename, or will mark the change 233 as WIP until it has been. 234 235## Testing my changes 236 237Each of the following must succeed when executed in order. Note that to avoid 238[googletest bug #4232][googletest-issue-4232] you must avoid using GCC 12 239(shipped in Debian Bookworm). 240 241[googletest-issue-4232]: https://github.com/google/googletest/issues/4232 242 243- [ ] `meson setup -Dabi-compliance-check=disabled build` 244- [ ] `meson compile -C build && meson test -C build` 245 246- [ ] `meson configure --buildtype=release build` 247- [ ] `meson compile -C build && meson test -C build` 248 249- [ ] `meson configure --buildtype=debug build` 250- [ ] `meson configure -Dabi=deprecated,stable build` 251- [ ] `meson compile -C build && meson test -C build` 252 253This process is captured in `scripts/pre-submit` for automation. 254