build: tidy up local lseek() mappings

- stop redefining system symbol `lseek`, by introducing `curl_lseek()`.
- handle AmigaOS quirk within the macro mapping.
- add missing parenthesis to `LSEEK_ERROR` values.
- tool_util: use curl `lseek` macros in `tool_ftruncate64()`.
- move `LSEEK_ERROR` to right-hand side of if expressions.
- checksrc: disallow direct uses of `_lseeki64`, `llseek`, `lseek`.

Closes #20488

docs/internals/CODE_STYLE.md

@@ -332,6 +332,7 @@ makes us write better code.
 This is the full list of functions generally banned.
 
     _access
+    _lseeki64
     _mbscat
     _mbsncat
     _open
@@ -367,6 +368,7 @@ This is the full list of functions generally banned.
     getaddrinfo
     gets
     gmtime
+    llseek
     LoadLibrary
     LoadLibraryA
     LoadLibraryEx
@@ -374,6 +376,7 @@ This is the full list of functions generally banned.
     LoadLibraryExW
     LoadLibraryW
     localtime
+    lseek
     malloc
     mbstowcs
     MoveFileEx

lib/curl_setup.h

@@ -490,28 +490,28 @@
 #  include <sys/types.h>
 #  include <sys/stat.h>
    /* Large file (>2Gb) support using Win32 functions. */
-#  undef  lseek
-#  define lseek(fdes, offset, whence)  _lseeki64(fdes, offset, whence)
 #  undef  fstat
-#  define fstat(fdes, stp)             _fstati64(fdes, stp)
-#  define struct_stat                  struct _stati64
-#  define LSEEK_ERROR                  (__int64)-1
+#  define fstat(fdes, stp)                _fstati64(fdes, stp)
+#  define struct_stat                     struct _stati64
+#  define curl_lseek                      _lseeki64
+#  define LSEEK_ERROR                     ((__int64)-1)
 #elif defined(__DJGPP__)
    /* Requires DJGPP 2.04 */
 #  include <unistd.h>
-#  undef  lseek
-#  define lseek(fdes, offset, whence)  llseek(fdes, offset, whence)
-#  define LSEEK_ERROR                  (offset_t)-1
+#  define curl_lseek                      llseek
+#  define LSEEK_ERROR                     ((offset_t)-1)
+#elif defined(__AMIGA__)
+#  define curl_lseek(fd, offset, whence)  lseek(fd, (off_t)(offset), whence)
+#  define LSEEK_ERROR                     ((off_t)-1)
+#else
+#  define curl_lseek                      lseek
+#  define LSEEK_ERROR                     ((off_t)-1)
 #endif
 
 #ifndef struct_stat
 #define struct_stat struct stat
 #endif
 
-#ifndef LSEEK_ERROR
-#define LSEEK_ERROR (off_t)-1
-#endif
-
 #ifndef SIZEOF_TIME_T
 /* assume default size of time_t to be 32 bits */
 #define SIZEOF_TIME_T 4

lib/file.c

@@ -517,13 +517,8 @@ static CURLcode file_do(struct Curl_easy *data, bool *done)
 
   if(data->state.resume_from) {
     if(!S_ISDIR(statbuf.st_mode)) {
-#ifdef __AMIGA__
       if(data->state.resume_from !=
-         lseek(fd, (off_t)data->state.resume_from, SEEK_SET))
-#else
-      if(data->state.resume_from !=
-         lseek(fd, data->state.resume_from, SEEK_SET))
-#endif
+         curl_lseek(fd, data->state.resume_from, SEEK_SET))
         return CURLE_BAD_DOWNLOAD_RESUME;
     }
     else {

scripts/checksrc.pl

@@ -49,6 +49,7 @@ my @ignore_line;
 
 my %banfunc = (
     "_access" => 1,
+    "_lseeki64" => 1,
     "_mbscat" => 1,
     "_mbsncat" => 1,
     "_open" => 1,
@@ -84,6 +85,7 @@ my %banfunc = (
     "getaddrinfo" => 1,
     "gets" => 1,
     "gmtime" => 1,
+    "llseek" => 1,
     "LoadLibrary" => 1,
     "LoadLibraryA" => 1,
     "LoadLibraryEx" => 1,
@@ -91,6 +93,7 @@ my %banfunc = (
     "LoadLibraryExW" => 1,
     "LoadLibraryW" => 1,
     "localtime" => 1,
+    "lseek" => 1,
     "malloc" => 1,
     "mbstowcs" => 1,
     "MoveFileEx" => 1,

src/tool_cb_see.c

@@ -61,13 +61,13 @@ int tool_seek_cb(void *userdata, curl_off_t offset, int whence)
       /* this code path does not support other types */
       return CURL_SEEKFUNC_FAIL;
 
-    if(LSEEK_ERROR == lseek(per->infd, 0, SEEK_SET))
+    if(curl_lseek(per->infd, 0, SEEK_SET) == LSEEK_ERROR)
       /* could not rewind to beginning */
       return CURL_SEEKFUNC_FAIL;
 
     while(left) {
       long step = (left > OUR_MAX_SEEK_O) ? OUR_MAX_SEEK_L : (long)left;
-      if(LSEEK_ERROR == lseek(per->infd, step, SEEK_CUR))
+      if(curl_lseek(per->infd, step, SEEK_CUR) == LSEEK_ERROR)
         /* could not seek forwards the desired amount */
         return CURL_SEEKFUNC_FAIL;
       left -= step;
@@ -76,11 +76,7 @@ int tool_seek_cb(void *userdata, curl_off_t offset, int whence)
   }
 #endif
 
-#ifdef __AMIGA__
-  if(LSEEK_ERROR == lseek(per->infd, (off_t)offset, whence))
-#else
-  if(LSEEK_ERROR == lseek(per->infd, offset, whence))
-#endif
+  if(curl_lseek(per->infd, offset, whence) == LSEEK_ERROR)
     /* could not rewind, the reason is in errno but errno is just not portable
        enough and we do not actually care that much why we failed. We will let
        libcurl know that it may try other means if it wants to. */

src/tool_util.c

@@ -86,7 +86,7 @@ int tool_ftruncate64(int fd, curl_off_t where)
 {
   intptr_t handle = _get_osfhandle(fd);
 
-  if(_lseeki64(fd, where, SEEK_SET) < 0)
+  if(curl_lseek(fd, where, SEEK_SET) == LSEEK_ERROR)
     return -1;
 
   if(!SetEndOfFile((HANDLE)handle))

tests/server/tftpd.c

@@ -454,7 +454,7 @@ static ssize_t write_behind(struct testcase *test, int convert)
     c = *p++;                     /* pick up a character */
     if(prevchar == '\r') {        /* if prev char was cr */
       if(c == '\n')               /* if have cr,lf then just */
-        lseek(test->ofile, -1, SEEK_CUR); /* smash lf on top of the cr */
+        curl_lseek(test->ofile, -1, SEEK_CUR); /* smash lf on top of the cr */
       else if(c == '\0')          /* if have cr,nul then */
         goto skipit;              /* just skip over the putc */
       /* else just fall through and allow it */