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fix(strings): non fatal errors for [NULL] safety in vim_snprintf

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context: vim_snprintf provides a "portable" replacement for a system
vsnprintf(). However we rely on system vsnprintf() in places. This
is quite arbitrary. I want to use system vsnprintf() only, and
reduce the machinery in string.c for typval printf only, which will
delet a lot of duplicated code.

The biggest hurdle here is not "portably" (we only support sane c
runtimes) but the following discrepancy: standard libc printf()
considers NULL args to %s to be undefined behavior strictly
while vim_snprintf() _defacto_ allows this by replacement to "[NULL]"

IMO, this should be seen as "graceful" error handling (nicer than crashing
on the user), not a valid means to have the string "[NULL]" intentionally
be shoved in the users face. more robust code should explicitly
check for NULL and replace it with a _appropriate_ fallback for
the situation, depending on what a NULL string actually means in the
context (unnamed buffer? anonymous namespace? global augroup?)

soo, this PR provides the most _gently_ incremental nudge towards
considering this case again as an error one could possible imagine.
If sanitizers are complied in, this minor incursion gets printed
into the sanitizers' log as a "report-and-continue" error with a
traceback. This doesn't annoy the end user or "stop the world"
in the test suite, but the CI will see the reported error and
fail the build, just like other non-fatal CI errors.
This commit is contained in:
bfredl
2026-09-07 13:39:56 +02:00
parent 45b645718c
commit 97660307f5
6 changed files with 20 additions and 19 deletions
Download Patch File Download Diff File Expand all files Collapse all files

17
src/nvim/lua/executor.c
View File

@@ -1131,12 +1131,6 @@ static void nlua_print_event(void **argv)
static int nlua_print(lua_State *const lstate)
FUNC_ATTR_NONNULL_ALL
{
#define PRINT_ERROR(msg) \
do { \
errmsg = msg; \
errmsg_len = sizeof(msg) - 1; \
goto nlua_print_error; \
} while (0)
const int nargs = lua_gettop(lstate);
lua_getglobal(lstate, "tostring");
const char *errmsg = NULL;
@@ -1148,22 +1142,21 @@ static int nlua_print(lua_State *const lstate)
lua_pushvalue(lstate, -1); // tostring
lua_pushvalue(lstate, curargidx); // arg
// Do not use nlua_pcall here to avoid duplicate stack trace information
if (lua_pcall(lstate, 1, 1, 0)) {
errmsg = lua_tolstring(lstate, -1, &errmsg_len);
if (lua_pcall(lstate, 1, 1, 0) || lua_type(lstate, -1) != LUA_TSTRING) {
// NB: this might try tostring once more to print a weird error from
// a __tostring methamethod but we stop after that.
errmsg = nlua_get_error(lstate, &errmsg_len);
goto nlua_print_error;
}
size_t len;
const char *const s = lua_tolstring(lstate, -1, &len);
if (s == NULL) {
PRINT_ERROR("<Unknown error: lua_tolstring returned NULL for tostring result>");
}
ga_concat_len(&msg_ga, s, len);
if (curargidx < nargs) {
ga_append(&msg_ga, ' ');
}
lua_pop(lstate, 1);
}
#undef PRINT_ERROR
ga_append(&msg_ga, NUL);
lua_getfield(lstate, LUA_REGISTRYINDEX, "nvim.thread");

3
src/nvim/sign.c
View File

@@ -264,7 +264,8 @@ static void sign_list_placed(buf_T *rbuf, char *group)
while (buf != NULL && !got_int) {
if (buf_has_signs(buf)) {
msg_putchar('\n');
vim_snprintf(lbuf, MSG_BUF_LEN, _("Signs for %s:"), buf->b_fname);
const char *fname = buf->b_fname ? buf->b_fname : _("Untitled");
snprintf(lbuf, MSG_BUF_LEN, _("Signs for %s:"), fname);
msg_puts_hl(lbuf, HLF_D, false);
}

7
src/nvim/strings.c
View File

@@ -1784,6 +1784,13 @@ int vim_vsnprintf_typval(char *str, size_t str_m, const char *fmt, va_list ap_st
va_arg(ap, const char *)));
if (!str_arg) {
#ifdef ENABLE_ASAN_UBSAN
// this is only for vsnprintf() emulation, v:_null_string handled in tv_str()
if (!tvs) {
__sanitizer_print_stack_trace();
__sanitizer_report_error_summary("SUMMARY: NULL argument passed to %s");
}
#endif
str_arg = "[NULL]";
str_arg_l = 6;
} else if (!precision_specified) {

6
test/functional/lua/overrides_spec.lua
View File

@@ -59,15 +59,15 @@ describe('print', function()
eq('', exec_capture('luafile ' .. fname))
-- TODO(bfredl): these look weird, print() should not use "E5114:" style errors..
eq(
'Vim(lua):E5108: Lua: E5114: Converting print argument #2: [NULL]',
'Vim(lua):E5108: Lua: E5114: Converting print argument #2: nil',
pcall_err(command, 'lua print("foo", v_nilerr, "bar")')
)
eq(
'Vim(lua):E5108: Lua: E5114: Converting print argument #2: Xtest-functional-lua-overrides-luafile:2: abc',
pcall_err(command, 'lua print("foo", v_abcerr, "bar")')
)
eq(
'Vim(lua):E5108: Lua: E5114: Converting print argument #2: <Unknown error: lua_tolstring returned NULL for tostring result>',
matches(
'^Vim%(lua%):E5108: Lua: E5114: Converting print argument #2: table: 0x%x+$',
pcall_err(command, 'lua print("foo", v_tblout, "bar")')
)
end)

2
test/functional/ui/sign_spec.lua
View File

@@ -451,7 +451,7 @@ describe('Signs', function()
{3: }|
:sign place |
{100:--- Signs ---} |
{18:Signs for [NULL]:} |
{18:Signs for Untitled:} |
line=1 id=100000 name=piet priority=10 |
{6:Press ENTER or type command to continue}^ |
]])

4
test/old/testdir/test_signs.vim
View File

@@ -61,7 +61,7 @@ func Test_sign()
" Check placed signs
let a=execute('sign place')
call assert_equal("\n--- Signs ---\nSigns for [NULL]:\n" .
call assert_equal("\n--- Signs ---\nSigns for Untitled:\n" .
\ " line=3 id=41 name=Sign1 priority=10", a)
" Unplace the sign and try jumping to it again should fail.
@@ -90,7 +90,7 @@ func Test_sign()
sign place 77 line=9 name=Sign2
let a=execute('sign place')
" Nvim: sign line clamped to buffer length
call assert_equal("\n--- Signs ---\nSigns for [NULL]:\n" .
call assert_equal("\n--- Signs ---\nSigns for Untitled:\n" .
\ " line=4 id=77 name=Sign2 priority=10", a)
sign unplace *