PRVM: optimise string arguments

Adds a warning for when QC tries to create a string that's too long
(previously this caused silent truncation).

Signed-off-by: bones_was_here <bones_was_here@xonotic.au>

diff --git a/prvm_cmds.c b/prvm_cmds.c
index a86783fea5117e21dc1237a8c914e2dec08a068b..dcf2dccfc61691dc2da329884b435ffc156db7d6 100644 (file)
--- a/prvm_cmds.c
+++ b/prvm_cmds.c
@@ -271,20 +271,41 @@ void VM_RemoveEdictSkeleton(prvm_prog_t *prog, prvm_edict_t *ed)
 //============================================================================
 //BUILT-IN FUNCTIONS
 
-void VM_VarString(prvm_prog_t *prog, int first, char *out, int outlength)
+#ifdef WIN32
+       // memccpy() is standard in POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD, C23.
+       // Microsoft supports it, but apparently complains if we use it.
+       #pragma warning(disable : 4996)
+#endif
+size_t VM_VarString(prvm_prog_t *prog, int first, char *out, size_t outsize)
 {
        int i;
        const char *s;
-       char *outend;
+       char *p;
+       char *outend = out + outsize - 1;
 
-       outend = out + outlength - 1;
+       // bones_was_here: && out < outend improves perf significantly in some tests that don't trigger the warning,
+       // which seems odd, surely it would only help when the warning is printed?
        for (i = first;i < prog->argc && out < outend;i++)
        {
                s = PRVM_G_STRING((OFS_PARM0+i*3));
-               while (out < outend && *s)
-                       *out++ = *s++;
+               if (*s)
+               {
+                       // like dp_stpecpy but with a VM_Warning for use with `prvm_backtraceforwarnings 1`
+                       p = (char *)memccpy(out, s, '\0', (outend + 1) - out);
+                       if (p)
+                               out = p - 1;
+                       else
+                       {
+                               VM_Warning(prog, "%zu of %zu bytes available, will truncate %zu byte string \"%s\"\n", outend - out, outsize - 1, strlen(s), s);
+                               out = outend;
+                               *out = '\0';
+                       }
+               }
+               else
+                       *out = '\0';
        }
-       *out++ = 0;
+
+       return outsize - ((outend + 1) - out);
 }
 
 /*
@@ -2026,7 +2047,7 @@ fputs(float fhandle, string s)
 //void(float fhandle, string s) fputs = #113; // writes a line of text to the end of the file
 void VM_fputs(prvm_prog_t *prog)
 {
-       int stringlength;
+       size_t stringlength;
        char string[VM_TEMPSTRING_MAXSIZE];
        int filenum;
 
@@ -2043,8 +2064,8 @@ void VM_fputs(prvm_prog_t *prog)
                VM_Warning(prog, "VM_fputs: no such file handle %i (or file has been closed) in %s\n", filenum, prog->name);
                return;
        }
-       VM_VarString(prog, 1, string, sizeof(string));
-       if ((stringlength = (int)strlen(string)))
+       stringlength = VM_VarString(prog, 1, string, sizeof(string));
+       if (stringlength)
                FS_Write(prog->openfiles[filenum], string, stringlength);
        if (developer_extra.integer)
                Con_DPrintf("fputs: %s: %s\n", prog->name, string);
@@ -2598,8 +2619,7 @@ void VM_strzone(prvm_prog_t *prog)
 
        VM_SAFEPARMCOUNT(1,VM_strzone);
 
-       VM_VarString(prog, 0, string, sizeof(string));
-       alloclen = strlen(string) + 1;
+       alloclen = VM_VarString(prog, 0, string, sizeof(string)) + 1;
        PRVM_G_INT(OFS_RETURN) = PRVM_AllocString(prog, alloclen, &out);
        memcpy(out, string, alloclen);
 }
@@ -4982,7 +5002,9 @@ static int chrchar_alpha(int i, int basec, int baset, int convc, int convt, int
 //bulk convert a string. change case or colouring.
 void VM_strconv (prvm_prog_t *prog)
 {
-       int ccase, redalpha, rednum, len, i;
+       int ccase, redalpha, rednum;
+       unsigned i;
+       size_t resbuf_len;
        unsigned char resbuf[VM_TEMPSTRING_MAXSIZE];
        unsigned char *result = resbuf;
 
@@ -4991,10 +5013,9 @@ void VM_strconv (prvm_prog_t *prog)
        ccase = (int) PRVM_G_FLOAT(OFS_PARM0);  //0 same, 1 lower, 2 upper
        redalpha = (int) PRVM_G_FLOAT(OFS_PARM1);       //0 same, 1 white, 2 red,  5 alternate, 6 alternate-alternate
        rednum = (int) PRVM_G_FLOAT(OFS_PARM2); //0 same, 1 white, 2 red, 3 redspecial, 4 whitespecial, 5 alternate, 6 alternate-alternate
-       VM_VarString(prog, 3, (char *) resbuf, sizeof(resbuf));
-       len = (int)strlen((char *) resbuf);
+       resbuf_len = VM_VarString(prog, 3, (char *) resbuf, sizeof(resbuf));
 
-       for (i = 0; i < len; i++, result++)     //should this be done backwards?
+       for (i = 0; i < resbuf_len; i++, result++)      //should this be done backwards?
        {
                if (*result >= '0' && *result <= '9')   //normal numbers...
                        *result = chrconv_number(*result, '0', rednum);
@@ -5121,10 +5142,12 @@ void VM_crc16(prvm_prog_t *prog)
 {
        float insensitive;
        char s[VM_TEMPSTRING_MAXSIZE];
+       size_t slen;
+
        VM_SAFEPARMCOUNTRANGE(2, 8, VM_crc16);
        insensitive = PRVM_G_FLOAT(OFS_PARM0);
-       VM_VarString(prog, 1, s, sizeof(s));
-       PRVM_G_FLOAT(OFS_RETURN) = (unsigned short) ((insensitive ? CRC_Block_CaseInsensitive : CRC_Block) ((unsigned char *) s, strlen(s)));
+       slen = VM_VarString(prog, 1, s, sizeof(s));
+       PRVM_G_FLOAT(OFS_RETURN) = (unsigned short) ((insensitive ? CRC_Block_CaseInsensitive : CRC_Block) ((unsigned char *) s, slen));
 }
 
 // #639 float(string digest, string data, ...) digest_hex
@@ -5137,14 +5160,13 @@ void VM_digest_hex(prvm_prog_t *prog)
        int outlen;
 
        char s[VM_TEMPSTRING_MAXSIZE];
-       int len;
+       size_t len;
 
        VM_SAFEPARMCOUNTRANGE(2, 8, VM_digest_hex);
        digest = PRVM_G_STRING(OFS_PARM0);
        if(!digest)
                digest = "";
-       VM_VarString(prog, 1, s, sizeof(s));
-       len = (int)strlen(s);
+       len = VM_VarString(prog, 1, s, sizeof(s));
 
        outlen = 0;
 

diff --git a/prvm_cmds.h b/prvm_cmds.h
index 048fcc56b523bee984a8410deba6d5d72ed2d987..46bab5d2f92a710248f8629a3e7cf85c52c2dc5b 100644 (file)
--- a/prvm_cmds.h
+++ b/prvm_cmds.h
@@ -216,7 +216,8 @@ float       getserverlistindexforkey(string key)
 
 // general functions
 void VM_CheckEmptyString (prvm_prog_t *prog, const char *s);
-void VM_VarString(prvm_prog_t *prog, int first, char *out, int outlength);
+/// Returns the length of the *out string excluding the \0 terminator.
+size_t VM_VarString(prvm_prog_t *prog, int first, char *out, size_t outsize);
 qbool PRVM_ConsoleCommand (prvm_prog_t *prog, const char *text, int *func, qbool preserve_self, int curself, double ptime, qbool prog_loaded, const char *error_message);
 prvm_stringbuffer_t *BufStr_FindCreateReplace (prvm_prog_t *prog, int bufindex, int flags, const char *format);
 void BufStr_Set(prvm_prog_t *prog, prvm_stringbuffer_t *stringbuffer, int strindex, const char *str);