gbranden pushed a commit to branch master
in repository groff.
commit 26b53881cbe6fe43a6cf50ff934cba34a725cb54
Author: G. Branden Robinson <[email protected]>
AuthorDate: Mon Mar 23 17:56:19 2026 -0500
[troff]: Fix `-Wformat-truncation` warnings.
* src/roff/troff/input.cpp (charinfo::dump):
* src/roff/troff/node.cpp (glyph_node::asciify): When preparing to
format the hexadecimal representation of a Unicode code point with
`get_unicode_code()`, prepare a buffer of sufficient size to store a
32-bit unsigned integer, as that's what snprintf(3)'s `%X` conversion
produces. It doesn't know that Unicode is only a 20.1-bit code. Even
if it did, our use of `int` to store the value fails to communicate
that constraint to snprintf(3).
Even the use of `int` a bit slippery of us, since it's a signed type
with a 31-bit significand. But libgroff's `glyph_to_unicode()`, which
`get_unicode_code()` calls, uses "-1" to signal an error in-band.
---
ChangeLog | 19 +++++++++++++++++++
src/roff/troff/input.cpp | 5 ++++-
src/roff/troff/node.cpp | 5 ++++-
3 files changed, 27 insertions(+), 2 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index 716ccf5cc..98045874f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,22 @@
+2026-03-23 G. Branden Robinson <[email protected]>
+
+ [troff]: Fix `-Wformat-truncation` warnings.
+
+ * src/roff/troff/input.cpp (charinfo::dump):
+ * src/roff/troff/node.cpp (glyph_node::asciify): When preparing
+ to format the hexadecimal representation of a Unicode code
+ point with `get_unicode_code()`, prepare a buffer of sufficient
+ size to store a 32-bit unsigned integer, as that's what
+ snprintf(3)'s `%X` conversion produces. It doesn't know that
+ Unicode is only a 20.1-bit code. Even if it did, our use of
+ `int` to store the value fails to communicate that constraint to
+ snprintf(3).
+
+ Even the use of `int` a bit slippery of us, since it's a signed
+ type with a 31-bit significand. But libgroff's
+ `glyph_to_unicode()`, which `get_unicode_code()` calls, uses
+ "-1" to signal an error in-band.
+
2026-03-23 G. Branden Robinson <[email protected]>
* configure.ac: Stop interpolating `GROFF_CXX_CHECK` macro.
diff --git a/src/roff/troff/input.cpp b/src/roff/troff/input.cpp
index f859bb569..91196b946 100644
--- a/src/roff/troff/input.cpp
+++ b/src/roff/troff/input.cpp
@@ -11223,7 +11223,10 @@ void charinfo::dump()
// Also see node.cpp::glyph_node::asciify().
int mapping = get_unicode_mapping();
if (mapping >= 0) {
- const size_t buflen = 6; // enough for five hex digits + '\0'
+ // All we need is `sizeof "10FFFF"` but GCC's
+ // "-Wformat-truncation" warning doesn't know that Unicode code
+ // points are limited in range.
+ const size_t buflen = sizeof "FFFFFFFF";
char hexbuf[buflen];
(void) memset(hexbuf, '\0', buflen);
(void) snprintf(hexbuf, buflen, "%.4X", mapping);
diff --git a/src/roff/troff/node.cpp b/src/roff/troff/node.cpp
index 9901a21d3..e4ea93d2f 100644
--- a/src/roff/troff/node.cpp
+++ b/src/roff/troff/node.cpp
@@ -3946,7 +3946,10 @@ void glyph_node::asciify(macro *m)
break;
default:
m->append_str("\\[u");
- const size_t buflen = sizeof "10FFFF";
+ // All we need is `sizeof "10FFFF"` but GCC's
+ // "-Wformat-truncation" warning doesn't know that Unicode
+ // code points are limited in range.
+ const size_t buflen = sizeof "FFFFFFFF";
char hexbuf[buflen];
(void) memset(hexbuf, '\0', buflen);
(void) snprintf(hexbuf, buflen, "%.4X", unicode_mapping);
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