[LLVM] [Support] Query the terminal width using ioctl() (llvm#143514)

On unix systems, we were trying to determine the terminal width using
the `COULMNS` environment variable. Unfortunately, `COLUMNS` is not 
exported by all shells and thus not available on some systems.

We were previously using `ioctl()` for this; fall back to doing so if `COLUMNS`
does not exist or does not store a positive integer.

This essentially reverts a3eb3d3 and
parts of https://reviews.llvm.org/D61326.

For more information, see llvm#139499.

Fixes llvm#139499.

Author: Sirraide

llvm/cmake/config-ix.cmake

@@ -19,20 +19,23 @@ if (ANDROID OR CYGWIN OR CMAKE_SYSTEM_NAME MATCHES "AIX|DragonFly|FreeBSD|Haiku|
   set(HAVE_SYS_MMAN_H 1)
   set(HAVE_SYSEXITS_H 1)
   set(HAVE_UNISTD_H 1)
+  set(HAVE_SYS_IOCTL_H 1)
 elseif (APPLE)
   set(HAVE_MACH_MACH_H 1)
   set(HAVE_MALLOC_MALLOC_H 1)
   set(HAVE_PTHREAD_H 1)
   set(HAVE_SYS_MMAN_H 1)
   set(HAVE_SYSEXITS_H 1)
   set(HAVE_UNISTD_H 1)
+  set(HAVE_SYS_IOCTL_H 1)
 elseif (WIN32)
   set(HAVE_MACH_MACH_H 0)
   set(HAVE_MALLOC_MALLOC_H 0)
   set(HAVE_PTHREAD_H 0)
   set(HAVE_SYS_MMAN_H 0)
   set(HAVE_SYSEXITS_H 0)
   set(HAVE_UNISTD_H 0)
+  set(HAVE_SYS_IOCTL_H 0)
 elseif (ZOS)
   # Confirmed in
   # https://github.com/llvm/llvm-project/pull/104706#issuecomment-2297109613
@@ -42,6 +45,7 @@ elseif (ZOS)
   set(HAVE_SYS_MMAN_H 1)
   set(HAVE_SYSEXITS_H 0)
   set(HAVE_UNISTD_H 1)
+  set(HAVE_SYS_IOCTL_H 1)
 else()
   # Other platforms that we don't promise support for.
   check_include_file(mach/mach.h HAVE_MACH_MACH_H)
@@ -50,6 +54,7 @@ else()
   check_include_file(sys/mman.h HAVE_SYS_MMAN_H)
   check_include_file(sysexits.h HAVE_SYSEXITS_H)
   check_include_file(unistd.h HAVE_UNISTD_H)
+  check_include_file(sys/ioctl.h HAVE_SYS_IOCTL_H)
 endif()
 
 if( UNIX AND NOT (APPLE OR BEOS OR HAIKU) )

llvm/include/llvm/Config/config.h.cmake

@@ -164,6 +164,9 @@
 /* Define to 1 if you have the <sys/mman.h> header file. */
 #cmakedefine HAVE_SYS_MMAN_H ${HAVE_SYS_MMAN_H}
 
+/* Define to 1 if you have the <sys/ioctl.h> header file. */
+#cmakedefine HAVE_SYS_IOCTL_H ${HAVE_SYS_IOCTL_H}
+
 /* Define to 1 if stat struct has st_mtimespec member .*/
 #cmakedefine HAVE_STRUCT_STAT_ST_MTIMESPEC_TV_NSEC ${HAVE_STRUCT_STAT_ST_MTIMESPEC_TV_NSEC}
 

llvm/lib/Support/Unix/Process.inc

@@ -34,6 +34,9 @@
 #ifdef HAVE_GETAUXVAL
 #include <sys/auxv.h>
 #endif
+#ifdef HAVE_SYS_IOCTL_H
+#include <sys/ioctl.h>
+#endif
 
 //===----------------------------------------------------------------------===//
 //=== WARNING: Implementation here must contain only generic UNIX code that
@@ -304,31 +307,40 @@ bool Process::FileDescriptorIsDisplayed(int fd) {
 #endif
 }
 
-static unsigned getColumns() {
+static unsigned getColumns(int FileID) {
   // If COLUMNS is defined in the environment, wrap to that many columns.
+  // This matches GCC.
   if (const char *ColumnsStr = std::getenv("COLUMNS")) {
     int Columns = std::atoi(ColumnsStr);
     if (Columns > 0)
       return Columns;
   }
 
-  // We used to call ioctl TIOCGWINSZ to determine the width. It is considered
-  // unuseful.
-  return 0;
+  // Some shells do not export COLUMNS; query the column count via ioctl()
+  // instead if it isn't available.
+  unsigned Columns = 0;
+
+#ifdef HAVE_SYS_IOCTL_H
+  struct winsize ws;
+  if (ioctl(FileID, TIOCGWINSZ, &ws) == 0)
+    Columns = ws.ws_col;
+#endif
+
+  return Columns;
 }
 
 unsigned Process::StandardOutColumns() {
   if (!StandardOutIsDisplayed())
     return 0;
 
-  return getColumns();
+  return getColumns(0);
 }
 
 unsigned Process::StandardErrColumns() {
   if (!StandardErrIsDisplayed())
     return 0;
 
-  return getColumns();
+  return getColumns(1);
 }
 
 static bool terminalHasColors() {