[Gcl-devel] mprotect question

[Aurelien Chanudet]

Hi,

I've tried compiling ACL2 on Mac OS X. Towards the end of the build, 
the compilation errors out, because mprotect (called from within GCL's 
sgc_mprotect) fails to promote a page whose max protection is 
read/write (not execute) to read/write/execute. A temporary fix is to 
promote the max protection to read/write/execute.

However, I'm wondering why this is happening. When GCL allocates memory 
pages, the initial max protection for these pages is set to 
read/write/execute. So, for a page's max protection to end up being 
read/write as in the afore-mentioned issue, someone must have change 
the max protection. My first question is : does GCL explicitly change a 
page's max protection ?

The stratified garbage collection code actually #defines 
PROT_READ_WRITE to be (PROT_READ | PROT_WRITE | PROT_EXEC). My second 
question is : where does the need for PROT_EXEC exactly originate from ?

Thanks,
Aurelien