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gh-121040: Use __attribute__((fallthrough)) (#121044)

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Fix warnings when using -Wimplicit-fallthrough compiler flag.

Annotate explicitly "fall through" switch cases with a new
_Py_FALLTHROUGH macro which uses __attribute__((fallthrough)) if
available. Replace "fall through" comments with _Py_FALLTHROUGH.

Add _Py__has_attribute() macro. No longer define __has_attribute()
macro if it's not defined. Move also _Py__has_builtin() at the top
of pyport.h.

Co-Authored-By: Nikita Sobolev <mail@sobolevn.me>
This commit is contained in:
Victor Stinner 2024-06-27 11:58:44 +02:00 • committed by GitHub
parent 4999e0bda0
commit 12af8ec864
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GPG key ID: B5690EEEBB952194
29 changed files with 131 additions and 104 deletions
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36
Python/pyhash.c
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@ -170,12 +170,12 @@ _Py_HashBytes(const void *src, Py_ssize_t len)
switch(len) {
/* ((hash << 5) + hash) + *p == hash * 33 + *p */
case 7: hash = ((hash << 5) + hash) + *p++; /* fallthrough */
case 6: hash = ((hash << 5) + hash) + *p++; /* fallthrough */
case 5: hash = ((hash << 5) + hash) + *p++; /* fallthrough */
case 4: hash = ((hash << 5) + hash) + *p++; /* fallthrough */
case 3: hash = ((hash << 5) + hash) + *p++; /* fallthrough */
case 2: hash = ((hash << 5) + hash) + *p++; /* fallthrough */
case 7: hash = ((hash << 5) + hash) + *p++; _Py_FALLTHROUGH;
case 6: hash = ((hash << 5) + hash) + *p++; _Py_FALLTHROUGH;
case 5: hash = ((hash << 5) + hash) + *p++; _Py_FALLTHROUGH;
case 4: hash = ((hash << 5) + hash) + *p++; _Py_FALLTHROUGH;
case 3: hash = ((hash << 5) + hash) + *p++; _Py_FALLTHROUGH;
case 2: hash = ((hash << 5) + hash) + *p++; _Py_FALLTHROUGH;
case 1: hash = ((hash << 5) + hash) + *p++; break;
default:
Py_UNREACHABLE();
@ -391,13 +391,13 @@ siphash13(uint64_t k0, uint64_t k1, const void *src, Py_ssize_t src_sz) {
t = 0;
pt = (uint8_t *)&t;
switch (src_sz) {
case 7: pt[6] = in[6]; /* fall through */
case 6: pt[5] = in[5]; /* fall through */
case 5: pt[4] = in[4]; /* fall through */
case 7: pt[6] = in[6]; _Py_FALLTHROUGH;
case 6: pt[5] = in[5]; _Py_FALLTHROUGH;
case 5: pt[4] = in[4]; _Py_FALLTHROUGH;
case 4: memcpy(pt, in, sizeof(uint32_t)); break;
case 3: pt[2] = in[2]; /* fall through */
case 2: pt[1] = in[1]; /* fall through */
case 1: pt[0] = in[0]; /* fall through */
case 3: pt[2] = in[2]; _Py_FALLTHROUGH;
case 2: pt[1] = in[1]; _Py_FALLTHROUGH;
case 1: pt[0] = in[0]; break;
}
b |= _le64toh(t);
@ -442,13 +442,13 @@ siphash24(uint64_t k0, uint64_t k1, const void *src, Py_ssize_t src_sz) {
t = 0;
pt = (uint8_t *)&t;
switch (src_sz) {
case 7: pt[6] = in[6]; /* fall through */
case 6: pt[5] = in[5]; /* fall through */
case 5: pt[4] = in[4]; /* fall through */
case 7: pt[6] = in[6]; _Py_FALLTHROUGH;
case 6: pt[5] = in[5]; _Py_FALLTHROUGH;
case 5: pt[4] = in[4]; _Py_FALLTHROUGH;
case 4: memcpy(pt, in, sizeof(uint32_t)); break;
case 3: pt[2] = in[2]; /* fall through */
case 2: pt[1] = in[1]; /* fall through */
case 1: pt[0] = in[0]; /* fall through */
case 3: pt[2] = in[2]; _Py_FALLTHROUGH;
case 2: pt[1] = in[1]; _Py_FALLTHROUGH;
case 1: pt[0] = in[0]; break;
}
b |= _le64toh(t);