| Issue |
208606
|
| Summary |
Apple clang version 21.0.0 (clang-2100.1.1.101) target arm64-apple-darwin25.5.0 optimizer causes crash.
|
| Labels |
clang
|
| Assignees |
|
| Reporter |
gwgill
|
Updating to clang 21 on ARM mac triggers a crash in my open source application when compiled with -02. This does not occur in previous versions or using other compilers such as gcc or cl. My C code uses struct type punning extensively to allow inheritance and polymorphism.
See attached example code distilled from the ArgyllCMS project gamut/gamut.c file.
Workaround is to lower optimization to -O or add -fno-strict-aliasing.
`
/* Example code that triggers -O2 crash in clang V21 -O2 */
/* By Graeme W. Gill */
/* Distilled from ArgyllCMS gamut/gamut.c */
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <fcntl.h>
#include <string.h>
#include <math.h>
/* ------------------------------------ */
/* Common base class of BSP nodes */
#define BSP_STRUCT \
int tag; /* Type of node, 1 = bsp node, 2 = triangle, 3 = list */ \
int id; /* Node id number (for debugging) */ \
static int node_id = 0;
struct _gbsp {
BSP_STRUCT
}; typedef struct _gbsp gbsp;
/* ------------------------------------ */
/* A BSP tree decision node */
struct _gbspn {
BSP_STRUCT
}; typedef struct _gbspn gbspn;
/* Allocate a BSP decision node structure */
gbspn *new_gbspn(void) {
gbspn *t;
t = (gbspn *) calloc(1, sizeof(gbspn));
t->id = node_id++;
t->tag = 1; /* bspn decision node */
return t;
}
/* ------------------------------------ */
/* A triangle in the surface mesh */
struct _gtri {
BSP_STRUCT
}; typedef struct _gtri gtri;
/* Allocate a triangle structure */
gtri *new_gtri(void) {
gtri *t;
t = (gtri *) calloc(1, sizeof(gtri));
t->id = node_id++;
t->tag = 2; /* Triangle */
return t;
}
/* ------------------------------------ */
/* A BSP tree triangle list node */
struct _gbspl {
BSP_STRUCT
int nt; /* Number of triangles in the list */
struct _gtri *t[]; /* List of triangles - allocated with struct */
}; typedef struct _gbspl gbspl;
gbspl *new_gbspl(void) {
gbspl *l;
int i;
int nt = 4;
l = (gbspl *) calloc(1, sizeof(gbspl) + nt * sizeof(gtri *));
l->id = node_id++;
l->tag = 3; /* bspl triangle list node */
l->nt = nt;
for (i = 0; i < nt; i++)
l->t[i] = new_gtri();
return l;
}
/* ------------------------------------ */
static gtri *radial_point_triang(
gbsp *np /* BSP node pointer we're at */
) {
gtri *rv;
if (np->tag == 1) { /* It's a BSP node */
gbspn *n = (gbspn *)np;
printf("This is a BSP node id = %d\n",n->id);
return NULL; /* Hmm */
} else { /* It's a triangle or list of triangles */
int nt; /* Number of triangles in list */
gtri **tpp; /* Pointer to list of triangles */
int i;
if (np->tag == 2) { /* It's a triangle, fake a list of 1 */
printf("This is a triangle id %d\n",np->id);
tpp = (gtri **)&np;
nt = 1;
} else if (np->tag == 3) { /* It's a triangle list */
gbspl *n = (gbspl *)np;
printf("This is a triangle list id %d\n",n->id);
tpp = n->t;
nt = n->nt;
}
for (i = 0; i < nt; i++, tpp++) {
gtri *t = *tpp;
printf(" list entry %d = id %d\n",i,t->id);
}
}
return NULL;
}
/* ------------------------------------ */
int
main(int argc, char *argv[]) {
gbspn *nd;
gbspl *tl;
gtri *tr;
nd = new_gbspn();
tl = new_gbspl();
tr = new_gtri();
radial_point_triang((gbsp *)nd);
radial_point_triang((gbsp *)tl);
radial_point_triang((gbsp *)tr); // This crashes with -O2
return 0;
}
`
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