gbranden pushed a commit to branch master
in repository groff.
commit 45409e003ae0bc60b5f663ec667c1c4a11638a30
Author: G. Branden Robinson <[email protected]>
AuthorDate: Wed Aug 7 02:56:27 2024 -0500
src/roff/troff/env.cpp: Slightly refactor.
* src/roff/troff/env.cpp (hyphenate): Slightly refactor. Reorder
equality comparison to avoid inadvertent lvalue assignment.
`memset()` the stack-allocated character array `hbuf` with null
terminators as a paranoid hedge. Rename `buf` to `bufp`, since it is
a pointer and moreover used as a cursor into the word that is a
candidate for hyphenation. Pointers and arrays are _not_ synonymous
in C/C++; see Chapter 4, _Expert C Programming: Deep C Secrets_, by
van der Linden (1994). Add assertions for further paranoia. Use
`static_cast` instead of C-style cast on dictionary values.
`memset()` the stack-allocated integer array `word` with zeroes.
Also add annotations, including null pointers with `nullptr` comment to
ease any future transition to C++11, which defines it as a keyword.
---
ChangeLog | 14 ++++++++++++++
src/roff/troff/env.cpp | 51 ++++++++++++++++++++++++++++++++++++--------------
2 files changed, 51 insertions(+), 14 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index 8aba5f2d2..de9cd6205 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,17 @@
+2024-08-07 G. Branden Robinson <[email protected]>
+
+ * src/roff/troff/env.cpp (hyphenate): Slightly refactor.
+ Reorder equality comparison to avoid inadvertent lvalue
+ assignment. `memset()` the stack-allocated character array
+ `hbuf` with null terminators as a paranoid hedge. Rename `buf`
+ to `bufp`, since it is a pointer and moreover used as a cursor
+ into the word that is a candidate for hyphenation. Pointers and
+ arrays are _not_ synonymous in C/C++; see Chapter 4, _Expert C
+ Programming: Deep C Secrets_, by van der Linden (1994). Add
+ assertions for further paranoia. Use `static_cast` instead of
+ C-style cast on dictionary values. `memset()` the
+ stack-allocated integer array `word` with zeroes.
+
2024-08-07 G. Branden Robinson <[email protected]>
[troff]: Fix code style nits.
diff --git a/src/roff/troff/env.cpp b/src/roff/troff/env.cpp
index 5e3371cff..ca69e38fa 100644
--- a/src/roff/troff/env.cpp
+++ b/src/roff/troff/env.cpp
@@ -4225,30 +4225,50 @@ void init_env_requests()
register_dictionary.define("st", new variable_reg(&st_reg_contents));
}
+// Appendix H of _The TeXbook_ is useful background for the following.
+
void hyphenate(hyphen_list *h, unsigned flags)
{
if (!current_language)
return;
while (h) {
- while (h && h->hyphenation_code == 0)
+ while (h && (0 == h->hyphenation_code))
h = h->next;
int len = 0;
+ // Locate hyphenable points within a (subset of) an input word.
+ //
+ // We first look up the word in the environment's hyphenation
+ // exceptions dictionary; its keys are C strings, so the buffer
+ // `hbuf` that holds our word needs to be null terminated and we
+ // allocate a byte for that. If the lookup fails, we apply the
+ // hyphenation patterns, which require that the word be bracketed at
+ // each end with a dot ('.'), so we allocate two further bytes.
+ //
+ // `hbuf` can be thought of as a mapping of the letters of the input
+ // word to the hyphenation codes that correspond to each letter.
+ // The hyphenation codes are normalized; "AbBoT" becomes "abbot".
+ //
+ // We can hyphenate words longer than WORD_MAX, but WORD_MAX is the
+ // maximum size of the "window" inside a word within which we apply
+ // the hyphenation patterns to determine a break point.
char hbuf[WORD_MAX + 2 + 1];
- char *buf = hbuf + 1;
+ (void) memset(hbuf, '\0', sizeof hbuf);
+ char *bufp = hbuf + 1;
hyphen_list *tem;
for (tem = h; tem && len < WORD_MAX; tem = tem->next) {
if (tem->hyphenation_code != 0)
- buf[len++] = tem->hyphenation_code;
+ bufp[len++] = tem->hyphenation_code;
else
break;
}
hyphen_list *nexth = tem;
if (len >= 2) {
- // check `.hw' entries
- buf[len] = 0;
- unsigned char *pos
- = (unsigned char *)current_language->exceptions.lookup(buf);
- if (pos != 0) {
+ // Check hyphenation exceptions defined with `hw` request.
+ assert((bufp + len) < (hbuf + sizeof hbuf));
+ bufp[len] = '\0';
+ unsigned char *pos = static_cast<unsigned char *>(
+ current_language->exceptions.lookup(bufp));
+ if (pos != 0 /* nullptr */) {
int j = 0;
int i = 1;
for (tem = h; tem != 0 /* nullptr */; tem = tem->next, i++)
@@ -4258,12 +4278,14 @@ void hyphenate(hyphen_list *h, unsigned flags)
}
}
else {
- // check `\hyphenation' entries from pattern files;
- // such entries are marked with a trailing space
- buf[len] = ' ';
- buf[len + 1] = 0;
- pos = (unsigned char *)current_language->exceptions.lookup(buf);
- if (pos != 0) {
+ // Check `\hyphenation' entries from pattern files; such entries
+ // are marked with a trailing space.
+ assert((hbuf + len + 1) < (hbuf + sizeof hbuf));
+ bufp[len] = ' ';
+ bufp[len + 1] = '\0';
+ pos = static_cast<unsigned char *>(
+ current_language->exceptions.lookup(bufp));
+ if (pos != 0 /* nullptr */) {
int j = 0;
int i = 1;
tem = h;
@@ -4294,6 +4316,7 @@ void hyphenate(hyphen_list *h, unsigned flags)
else {
hbuf[0] = hbuf[len + 1] = '.';
int num[WORD_MAX + 2 + 1];
+ (void) memset(num, 0, sizeof num);
current_language->patterns.hyphenate(hbuf, len + 2, num);
// The position of a hyphenation point gets marked with an odd
// number. Example:
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