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pfalconpfalcon
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unix/main: When preparing sys.path, allocate exact strings on uPy heap.
Due to the way modern compilers work (allocating space for stack vars once at tha start of function, and deallocating once on exit from), using intermediate stack buffer of big size caused blockage of 4K (PATH_MAX) on stack for the entire duration of MicroPython execution.
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Lines changed: 6 additions & 4 deletions

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‎unix/main.c‎

Lines changed: 6 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -444,10 +444,12 @@ MP_NOINLINE int main_(int argc, char **argv) {
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}
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if (p[0] == '~' && p[1] == '/' && home != NULL) {
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// Expand standalone ~ to $HOME
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CHECKBUF(buf, PATH_MAX);
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CHECKBUF_APPEND(buf, home, strlen(home));
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CHECKBUF_APPEND(buf, p + 1, (size_t)(p1 - p - 1));
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path_items[i] = MP_OBJ_NEW_QSTR(qstr_from_strn(buf, CHECKBUF_LEN(buf)));
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int home_l = strlen(home);
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vstr_t vstr;
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vstr_init(&vstr, home_l + (p1 - p - 1) + 1);
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vstr_add_strn(&vstr, home, home_l);
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vstr_add_strn(&vstr, p + 1, p1 - p - 1);
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path_items[i] = mp_obj_new_str_from_vstr(&mp_type_str, &vstr);
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} else {
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path_items[i] = MP_OBJ_NEW_QSTR(qstr_from_strn(p, p1 - p));
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}

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