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Commita73952b

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Add check on initial and boot values when loading GUCs
This commit adds a function to perform a cross-check between the initialvalue of the C declaration associated to a GUC and its actual bootvalue in assert-enabled builds. The purpose of this is to preventanybody reading these C declarations from being fooled by mismatchedvalues before they are loaded at program startup.The following rules apply depending on the GUC type:* bool - can be false, or same as boot_val.* int - can be 0, or same as the boot_val.* real - can be 0.0, or same as the boot_val.* string - can be NULL, or strcmp'd equal to the boot_val.* enum - equal to the boot_val.This is done for the system as well custom GUCs loaded by externalmodules, which may require extension developers to adapt the Cdeclaration of the variables used by these GUCs (testing this changewith some of my own modules has allowed me to catch some stupid typos,FWIW). This may finish by being a bad experiment depending on thefeedbcak received, but let's see how it goes.Author: Peter SmithReviewed-by: Nathan Bossart, Tom Lane, Michael Paquier, Justin PryzbyDiscussion:https://postgr.es/m/CAHut+PtHE0XSfjjRQ6D4v7+dqzCw=d+1a64ujra4EX8aoc_Z+w@mail.gmail.com
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  • src/backend/utils/misc

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‎src/backend/utils/misc/guc.c

Lines changed: 89 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1382,6 +1382,89 @@ check_GUC_name_for_parameter_acl(const char *name)
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return false;
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}
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/*
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* Routine in charge of checking that the initial value of a GUC is the
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* same when declared and when loaded to prevent anybody looking at the
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* C declarations of these GUCS from being fooled by mismatched values.
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*
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* The following validation rules apply:
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* bool - can be false, otherwise must be same as the boot_val
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* int - can be 0, otherwise must be same as the boot_val
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* real - can be 0.0, otherwise must be same as the boot_val
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* string - can be NULL, otherwise must be strcmp equal to the boot_val
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* enum - must be same as the boot_val
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*/
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#ifdefUSE_ASSERT_CHECKING
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staticbool
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check_GUC_init(structconfig_generic*gconf)
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{
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switch (gconf->vartype)
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{
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casePGC_BOOL:
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{
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structconfig_bool*conf= (structconfig_bool*)gconf;
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if (*conf->variable&& !conf->boot_val)
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{
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elog(LOG,"GUC (PGC_BOOL) %s, boot_val=%d, C-var=%d",
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conf->gen.name,conf->boot_val,*conf->variable);
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return false;
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}
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break;
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}
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casePGC_INT:
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{
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structconfig_int*conf= (structconfig_int*)gconf;
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if (*conf->variable!=0&&*conf->variable!=conf->boot_val)
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{
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elog(LOG,"GUC (PGC_INT) %s, boot_val=%d, C-var=%d",
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conf->gen.name,conf->boot_val,*conf->variable);
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return false;
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}
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break;
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}
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casePGC_REAL:
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{
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structconfig_real*conf= (structconfig_real*)gconf;
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if (*conf->variable!=0.0&&*conf->variable!=conf->boot_val)
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{
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elog(LOG,"GUC (PGC_REAL) %s, boot_val=%g, C-var=%g",
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conf->gen.name,conf->boot_val,*conf->variable);
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return false;
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}
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break;
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}
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casePGC_STRING:
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{
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structconfig_string*conf= (structconfig_string*)gconf;
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if (*conf->variable!=NULL&&strcmp(*conf->variable,conf->boot_val)!=0)
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{
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elog(LOG,"GUC (PGC_STRING) %s, boot_val=%s, C-var=%s",
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conf->gen.name,conf->boot_val ?conf->boot_val :"<null>",*conf->variable);
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return false;
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}
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break;
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}
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casePGC_ENUM:
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{
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structconfig_enum*conf= (structconfig_enum*)gconf;
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if (*conf->variable!=conf->boot_val)
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{
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elog(LOG,"GUC (PGC_ENUM) %s, boot_val=%d, C-var=%d",
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conf->gen.name,conf->boot_val,*conf->variable);
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return false;
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}
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break;
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}
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}
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return true;
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}
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#endif
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/*
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* Initialize GUC options during program startup.
@@ -1413,6 +1496,9 @@ InitializeGUCOptions(void)
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hash_seq_init(&status,guc_hashtab);
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while ((hentry= (GUCHashEntry*)hash_seq_search(&status))!=NULL)
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{
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/* Check mapping between initial and default value */
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Assert(check_GUC_init(hentry->gucvar));
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14161502
InitializeOneGUCOption(hentry->gucvar);
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}
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@@ -4654,6 +4740,9 @@ define_custom_variable(struct config_generic *variable)
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GUCHashEntry*hentry;
46554741
structconfig_string*pHolder;
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/* Check mapping between initial and default value */
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Assert(check_GUC_init(variable));
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46574746
/*
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* See if there's a placeholder by the same name.
46594748
*/

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