[llvm] 7f22cee - [gcov] Don't skip leading zeros when reading a string

[Fangrui Song via llvm-commits]

Author: Fangrui Song
Date: 2020-05-10T10:16:34-07:00
New Revision: 7f22ceeaae74911d97773644a1058659f329887e

URL: https://github.com/llvm/llvm-project/commit/7f22ceeaae74911d97773644a1058659f329887e
DIFF: https://github.com/llvm/llvm-project/commit/7f22ceeaae74911d97773644a1058659f329887e.diff

LOG: [gcov] Don't skip leading zeros when reading a string

Even a 2003 version of gcov_read_string does not have the behavior
described by rL204881. The wrong impression might come from
libclang_rt.profile (GCDAProfiling.c)'s corrupted output (since the
initial import rL144865). Note, the corrupted output crashes gcov.

Added: 
    

Modified: 
    llvm/include/llvm/ProfileData/GCOV.h

Removed: 
    


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diff  --git a/llvm/include/llvm/ProfileData/GCOV.h b/llvm/include/llvm/ProfileData/GCOV.h
index a8b8655f740f..1aabf3b65b62 100644
--- a/llvm/include/llvm/ProfileData/GCOV.h
+++ b/llvm/include/llvm/ProfileData/GCOV.h
@@ -187,12 +187,9 @@ class GCOVBuffer {
   }
 
   bool readString(StringRef &Str) {
-    uint32_t Len = 0;
-    // Keep reading until we find a non-zero length. This emulates gcov's
-    // behaviour, which appears to do the same.
-    while (Len == 0)
-      if (!readInt(Len))
-        return false;
+    uint32_t Len;
+    if (!readInt(Len) || Len == 0)
+      return false;
     Len *= 4;
     if (Buffer->getBuffer().size() < Cursor + Len) {
       errs() << "Unexpected end of memory buffer: " << Cursor + Len << ".\n";