[PATCH] D47795: commandLineFitsWithinSystemLimits Overestimates System Limits

[Austin Belknap via Phabricator via llvm-commits]

dabelknap updated this revision to Diff 150152.
dabelknap added a comment.

Re-uploaded patch with full context.


https://reviews.llvm.org/D47795

Files:
  lib/Support/Unix/Program.inc


Index: lib/Support/Unix/Program.inc
===================================================================
--- lib/Support/Unix/Program.inc
+++ lib/Support/Unix/Program.inc
@@ -434,13 +434,24 @@
 bool llvm::sys::commandLineFitsWithinSystemLimits(StringRef Program,
                                                   ArrayRef<const char *> Args) {
   static long ArgMax = sysconf(_SC_ARG_MAX);
+  // POSIX requires that _POSIX_ARG_MAX is 4096, which is the lowest possible
+  // value for ARG_MAX on a POSIX compliant system.
+  static long ArgMin = _POSIX_ARG_MAX;
+
+  // This the same baseline used by xargs.
+  long EffectiveArgMax = 128 * 1024;
+
+  if (EffectiveArgMax > ArgMax)
+    EffectiveArgMax = ArgMax;
+  else if (EffectiveArgMax < ArgMin)
+    EffectiveArgMax = ArgMin;
 
   // System says no practical limit.
   if (ArgMax == -1)
     return true;
 
   // Conservatively account for space required by environment variables.
-  long HalfArgMax = ArgMax / 2;
+  long HalfArgMax = EffectiveArgMax / 2;
 
   size_t ArgLength = Program.size() + 1;
   for (const char* Arg : Args) {


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