[llvm] [NFC] [Support] Fix warning when build with clang-cl on Windows. (PR #65387)

[Xiang Li via llvm-commits]

https://github.com/python3kgae updated https://github.com/llvm/llvm-project/pull/65387:

>From 2d68f51827af3266a43b15da6227122d77f9bc55 Mon Sep 17 00:00:00 2001
From: Xiang Li <python3kgae at outlook.com>
Date: Tue, 5 Sep 2023 13:04:42 -0400
Subject: [PATCH 1/3] [NFC] [Support] Fix warning when build with clang-cl on
 Windows.

Add const qualifier to avoid "cast from 'const char *' to 'char *' drops const qualifier [-Werror,-Wcast-qual]"

This will allow enable LLVM_ENABLE_WERROR when build with clang-cl on Windows.
---
 llvm/lib/Support/regcomp.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/llvm/lib/Support/regcomp.c b/llvm/lib/Support/regcomp.c
index 4e9082cec456961..e79c2e5591c0b88 100644
--- a/llvm/lib/Support/regcomp.c
+++ b/llvm/lib/Support/regcomp.c
@@ -190,8 +190,8 @@ static struct cname {
  * other clumsinesses
  */
 struct parse {
-	char *next;		/* next character in RE */
-	char *end;		/* end of string (-> NUL normally) */
+	const char *next;	/* next character in RE */
+	const char *end;	/* end of string (-> NUL normally) */
 	int error;		/* has an error been seen? */
 	sop *strip;		/* malloced strip */
 	sopno ssize;		/* malloced strip size (allocated) */
@@ -334,7 +334,7 @@ llvm_regcomp(llvm_regex_t *preg, const char *pattern, int cflags)
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wcast-qual"
 #endif /* __GNUC__ */
-	p->next = (char *)pattern;	/* convenience; we do not modify it */
+	p->next = pattern;	/* convenience; we do not modify it */
 #ifdef __GNUC__
 #pragma GCC diagnostic pop
 #endif /* __GNUC__ */
@@ -948,7 +948,7 @@ p_b_term(struct parse *p, cset *cs)
 static void
 p_b_cclass(struct parse *p, cset *cs)
 {
-	char *sp = p->next;
+	const char *sp = p->next;
 	struct cclass *cp;
 	size_t len;
 	const char *u;
@@ -1012,7 +1012,7 @@ static char			/* value of collating element */
 p_b_coll_elem(struct parse *p,
     int endc)			/* name ended by endc,']' */
 {
-	char *sp = p->next;
+	const char *sp = p->next;
 	struct cname *cp;
 	size_t len;
 
@@ -1056,8 +1056,8 @@ othercase(int ch)
 static void
 bothcases(struct parse *p, int ch)
 {
-	char *oldnext = p->next;
-	char *oldend = p->end;
+	const char *oldnext = p->next;
+	const char *oldend = p->end;
 	char bracket[3];
 
 	ch = (uch)ch;
@@ -1098,8 +1098,8 @@ ordinary(struct parse *p, int ch)
 static void
 nonnewline(struct parse *p)
 {
-	char *oldnext = p->next;
-	char *oldend = p->end;
+	const char *oldnext = p->next;
+	const char *oldend = p->end;
 	char bracket[4];
 
 	p->next = bracket;

>From 4fff4d10889b279ddb41765f7bb5040f76366af2 Mon Sep 17 00:00:00 2001
From: Xiang Li <python3kgae at outlook.com>
Date: Tue, 5 Sep 2023 15:06:12 -0400
Subject: [PATCH 2/3] Remove the gcc change for the cast-qual warning.

---
 llvm/lib/Support/regcomp.c | 8 --------
 1 file changed, 8 deletions(-)

diff --git a/llvm/lib/Support/regcomp.c b/llvm/lib/Support/regcomp.c
index e79c2e5591c0b88..49cd372369e45a4 100644
--- a/llvm/lib/Support/regcomp.c
+++ b/llvm/lib/Support/regcomp.c
@@ -329,15 +329,7 @@ llvm_regcomp(llvm_regex_t *preg, const char *pattern, int cflags)
 
 	/* set things up */
 	p->g = g;
-	/* suppress warning from the following explicit cast. */
-#ifdef __GNUC__
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wcast-qual"
-#endif /* __GNUC__ */
 	p->next = pattern;	/* convenience; we do not modify it */
-#ifdef __GNUC__
-#pragma GCC diagnostic pop
-#endif /* __GNUC__ */
 	p->end = p->next + len;
 	p->error = 0;
 	p->ncsalloc = 0;

>From f0e8459ed5d8fe9c1c5c059e3abaa2d7f5786fa2 Mon Sep 17 00:00:00 2001
From: Xiang Li <python3kgae at outlook.com>
Date: Tue, 12 Sep 2023 15:29:54 -0400
Subject: [PATCH 3/3] Merge other change from
 https://github.com/openbsd/src/commit/b81763002452802e4f7304ea60f121253bd94

---
 llvm/lib/Support/regcomp.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/llvm/lib/Support/regcomp.c b/llvm/lib/Support/regcomp.c
index 49cd372369e45a4..78c827d0314a5a1 100644
--- a/llvm/lib/Support/regcomp.c
+++ b/llvm/lib/Support/regcomp.c
@@ -1092,14 +1092,10 @@ nonnewline(struct parse *p)
 {
 	const char *oldnext = p->next;
 	const char *oldend = p->end;
-	char bracket[4];
+	static const char bracket[4] = {'^', '\n', ']', '\0'};
 
 	p->next = bracket;
 	p->end = bracket+3;
-	bracket[0] = '^';
-	bracket[1] = '\n';
-	bracket[2] = ']';
-	bracket[3] = '\0';
 	p_bracket(p);
 	assert(p->next == bracket+3);
 	p->next = oldnext;